Cell Molecules

Biology

1. Biosphere Land – water – atmosphere (inhabited by life).



2. Ecosystem Living thing and non-living thing with which life

interacts in particular area (forests or oceans or

deserts).



3. Community living different species in particular

ecosystem.



4. Population one species.



5. Organism one individual (Body).



6. Organs

7. Tissues

8. Cells

9. Organelles

10. Molecules

Molecules



1. Organic compounds

(macromolecules)

Carbohydrates, lipid, proteins, vitamins and nucleic acid



1. Inorganic compounds

(micromolecules)

Water and minerals

THE STRUCTURE AND FUNCTION

OF MACROMOLECULES









Polymer principles

And

Macromolecules

Introduction (Polymers principles)

• Cells link smaller organic molecules together to form larger

molecules.



• These larger molecules called macromolecules.





• The four major classes of macromolecules are: carbohydrates,

lipids, proteins, and nucleic acids.



• Most macromolecules are polymers

– Polymers consist of many similar or identical building blocks,

called monomers. Linked by covalent bonds.

• Covalent bonds are formed by a

dehydration reaction ‫.تفاعل نزع الماء‬

– One monomer provides a hydroxyl group and

the other provides a hydrogen to form water.

– This process requires energy and is aided by

enzymes.







‫ وبالعكس‬Vise versa

• The covalent bonds connecting monomers in a polymer are disassembled

‫ تـُكســر‬by hydrolysis (hydration) ‫. بإضافة الماء‬

َ

– In hydrolysis as the covalent bond is broken a

hydrogen atom and hydroxyl group from a split

water molecule attaches where the covalent

bond used to be.

– Hydrolysis reactions dominate the digestive

process, guided by specific enzymes.

(Carbohydrates, Lipids, Proteins and nucleic acids)









Mono-mer Di-mer Poly-mer

‫أحادى‬ ‫ثنائى‬ ‫عديد‬

Polymer is a long molecule consists of a chain of similar

building molecules (monomers) covalently bounded together.



Polymer can be built up ‫ يـُبـ َنى‬by linking its monomers by

ْ

dehydration (removing H2O).

َ

Polymer can be broken down ‫ يـُكســًر إلى‬to its monomers by

hydrolysis (adding H2O).

THE STRUCTURE AND FUNCTION

OF MACROMOLECULES







1- Carbohydrates

Fuel and Building Material (‫) مادة الطاقة و البناء‬





1. Sugars, the smallest carbohydrates, serve as fuel and carbon

sources

2. Polysaccharides, the polymers of sugars, have storage and

structural roles

Carbohydrates include sugars.

• Monosaccharides, are the simplest carbohydrates (simple sugars).

• Disaccharides, double sugars, consist of two monosaccharides joined

by dehydration.

• Polysaccharides, are polymers of many monosaccharides.

___________________



• Monosaccharides have a carbonyl group (C=O) and multiple hydroxyl

groups (O-H) .

– If the carbonly group is at the end of C chain, the sugar is called aldose

(aldehyde sugar), if not, the sugars is called ketose (Ketone sugar).

– Glucose called “aldose”, and fructose called “ketose”. They are structural

isomers.

1- Monosaccharides

Aldose Ketose

H O H

H OH

C C

Glucose Fructose

C6H12O6 H C OH O C6H12O6

C

OH C H OH H

C

H C OH H C OH



H C OH H C OH



H C OH H C OH



H H

Triose Sugar Tetrose Sugar Pentose Sugar Hexose Sugar







H

H OH



H O H O C

H O

C C C C O



H C OH H C OH H C OH OH C H



H C OH H C OH H C OH H C OH



H H C OH H C OH H C OH



H H C OH H OH

C

Types of monosaccharides, based

on the number of C atoms H H

• Monosaccharides are also classified by the number of carbons in the backbone.

– Glucose and other six carbon sugars are hexoses ‫.سداسى‬

– Five carbon backbones are pentoses ‫ خماسى‬and three carbon sugars are trioses ‫.ثالثى‬









Aldehyde

sugars









Ketone

sugars

Summary



Monosaccharides are classified into :-

A- Based on the location of C=O



Aldoses: are the monosaccharides of carbonyle group (C=O)

at the end of C chain (e.g. Glucose).



Ketoses: are the monosaccharides of C=O carbonyle

group within ‫ داخل‬the C chain (e.g. Fructose).





B- Based on the number of C in the skeleton

Triose (3C): e.g. Glyceraldehyde.

Pentose (5C): e.g. Ribose.

Hexose (6C): e.g. Glucose, Fructose and Galactose.

2- Disaccharides ‫السكر الثنائى‬



Consist of 2 monosaccharide molecules during a dehydration

reaction ‫.تفاعل نزع الماء‬



1- Maltose (malt sugar)



2(C6H12O6) C12H22O11 + H2O

2 Glucose Maltose

2- Lactose (milk sugar): consists of Glucose + Galactose.







3- Sucrose (table sugar): consists of Glucose + Fructose.

3- Polysaccharides ‫السكر العديد‬

Consist of few hundreds to few thousands of monosaccharides.







They are two types:

1- Storage ‫.تخزينية‬ Provide sugar for cell, when needs, by hydrolysis







2- Structural ‫.تركيبية‬ Serve as building materials for the organism

A)- Storage Polysaccharides

I- Starch ‫النشا‬

A storage polysaccharide of plants (within plastids).



It is consisted of thousands of α glucose molecules.

Thus, it gives glucose when hydrolysed ‫ بإضافة الماء‬by special enzymes

in human.

Potatos and grains are the major source of starch.

II- Glycogen



Stored in animal cells (e.g. liver and muscle cells in Human).



It is consisted of thousands of glucose molecules.









Thus, it gives glucose when hydrolysed.

B)- Structural Polysaccharides

I- Cellulose

It is the building material of plants (cell wall).



Forms the micro-fibrils and cell wall in plants.



It is consisted of thousands of β glucose molecules.









Human cannot digest it, but some bacteria and protozoa can (e.g.

in Termites and Cows stomach).

Arrangement

of cellulose

in plants

• The enzymes that digest starch cannot hydrolyze

the beta linkages in cellulose.





– Cellulose in our food passes through the digestive tract

and is eliminated in feces as “insoluble fiber”.





– As it travels through the digestive tract, it abrades ‫ يثير‬the

intestinal walls and stimulates the secretion of mucus.

• Some microbes can digest cellulose to its glucose

monomers through the use of cellulase enzymes.





• Many eukaryotic herbivores ‫ ,آكالت العشب‬like cows and

termites, have symbiotic relationships with

cellulolytic microbes, allowing them access to this

rich source of energy.

II- Chitin ‫الكيتين‬

It is the building material of the cuticle ‫ الجـلَيد‬in insects.

ُ



It is consisted of thousands of glucose molecules with a N atom

in one end.



It is used to manufacture the surgical threads.

Carbohydrates



No. of C atoms No. of sugar molecules









Triose (3C) Pentose (5C) Hexose (6C)

Glyceraldehyde Ribose Glucose









Monosaccharides Disaccharides Polysaccharides

Glucose, galactose & Fructose Maltose, Lactose & Sucrose





Location of Carbonyl Group



Storage Structural

Starch (in plants) Cellulose (in plants)

Aldose Ketose & &

Glycogen (in animals) Chitin (in insects)

C=O group C=O group

is Terminal in middle

THE STRUCTURE AND FUNCTION

OF MACROMOLECULES



3) Proteins :- Many Structures, Many Functions

1. A polypeptide is a polymer of amino acids connected in a specific sequence

2. A protein’s function depends on its specific conformation

3) Proteins

 Their functions include structural support, storage, transport of

other substances, intercellular signaling ‫ ,اإلشارات بين الخلوية‬movement,

defense against microbes and work as enzymes in the cell that

regulate metabolism ‫.األيض‬



 Humans have tens of thousands of different proteins, each with

their own structure and function.



 All protein polymers are constructed from ‫ تتركب من‬the same set of 20

monomers, called amino acids.



 Polymers of proteins are called polypeptides ‫.ببتيدات عديدة‬



 A protein consists of one or more polypeptides folded and coiled

into a specific conformation

- Monomer of amino acid includes a hydrogen atom, a carboxyl

group, an amino group, and a variable ‫ متغيرة‬R group (or side chain),

all covalently bonded to C atom.







General Formula H H O

of the Amino

Acid: N C C

H OH Carboxyl

Amino

group

R group

Side chain



- The side chain R links with ‫ ترتبط بـ‬different compounds

- Differences in R groups produce the 20 different amino acids.

- The physical and chemical characteristics ‫ صفات‬of the R group

determine ‫ تحدد‬the unique characteristics of a particular amino acid.

Amino acids ‫األحماض األمينية‬

1. Hydrophobic: the amino acids that have hydrophobic R groups

(non-polar).

2- Hydrophilic: the amino acids that have polar R groups, making

them hydrophilic.









3- Ionized: the amino acids with functional groups that are charged

(ionized) at cellular pH (7). So, some R groups are bases, others are

acids.

The Peptide Bond ‫الرابطة البيبتيدية‬

Peptide bond formed between the carboxyl group of one amino acid

and the amino group of the other by dehydration.







H H O H H O

N C C N C C

H OH H OH

R R

Dehydration

Peptide bond

‫نزع الماء‬



Amino acids Peptide Polypeptide (Protein)

• Amino acids are joined together when a dehydration reaction removes a

hydroxyl group from the carboxyl end of one amino acid and a hydrogen

from the amino group of another. The resulting covalent bond is called a

peptide bond.









• Repeating the process over and over ‫ عدة مرات‬creates a long polypeptide chain.

– At one end is an amino acid with a free amino group the (the N-terminus)

and at the other is an amino acid with a free carboxyl group the (the C-

terminus).

• The repeated sequence (N-C-C) is the polypeptide backbone.

• Attached to the backbone are the various R groups.

• Polypeptides range in size from a few monomers to thousands.

Levels of Protein Structure



• The folding ‫ إلتفاف‬of a protein from a chain of amino acids

occurs spontaneously ‫.ذاتيا‬



• There are three levels of structure:

primary ‫ ,أولى‬secondary ‫ ,ثانوى‬and tertiary ‫ ثالثى‬structure,

are used to organize the folding within a single peptide

chain.



• Quaternary ‫ رُباعى‬structure arises when two or more

polypeptides (proteins) join to form another kind of

protein.

1. Primary structure:



It is a single peptide

chain of amino acids.

– Lysozyme, an enzyme that

attacks bacteria, consists of a

polypeptide chain of 129

amino acids.





– A slight change ‫ تغيير طفيف‬in the

primary structure can affect a

protein’s conformation and

ability to function.

• Sickle cell disease ‫:خاليا الدم المنجلية‬

an abnormal hemoglobin because of a single amino acid

substitution ‫.تغيير‬

– These abnormal hemoglobin crystallize, deforming ‫ يكسر‬the red blood

ُ

cells and leading to clogs ‫ إنسداد‬in tiny blood vessels ‫.أوعية‬

2. The secondary structure:

Results from hydrogen bonds at regular intervals ‫ على أبعاد متساوية‬along

the polypeptide backbone.





A. Coils ‫( الحلزونى‬α-helix)

are typical shapes

that develop from

secondary structure





B. Folds (β-pleated sheets)

‫ .الشيت المجعـد‬Composed

ُ



of several parallel α-helix

coils attached by H bonds

An example for folds (β-pleated sheets) ‫:الشيت المُجعد‬

Is the structural properties of silk ‫ الحرير‬because of the presence of

so many hydrogen bonds makes each silk fiber stronger than steel.

3. Tertiary structure:

is determined by a variety of interactions among ‫ خالل‬R groups and

between R groups and the polypeptide backbone.



– These interactions include weak bonds like hydrogen bonds

among polar areas, ionic bonds between charged R groups,

and hydrophobic interactions and Van der Waals interactions

among hydrophobic R groups.





- Also include disulfide bridges,

strong covalent bonds that

form between the sulfhydryl

groups (SH) of cysteine

monomers, stabilize the

structure.

4- The quaternary structure:

Results from the aggregation ‫ تجمع‬of two or more

polypeptide chains.



Collagen is a fibrous protein of three polypeptides that are

supercoiled, and function in connective tissues.





Hemoglobin

is a globular protein with

two copies of two kinds

of polypeptides (2α and

2β).



Collagen Hemoglobin

The 4 forms of protein

Denaturation of protein ‫فرد البروتين‬

ْ









• It is the change of protein’s conformation in response to

‫ إستجابة لـ‬the physical and chemical conditions.





• For example, alterations ‫ تغيير‬in pH, salt concentration,

temperature, or other factors can denature ‫ يفرد‬a protein.

– These forces break the hydrogen bonds, ionic bonds, and

disulfide bridges that maintain the protein’s complicated shape.





• Some proteins can return to their original shape again

after denaturation, but others cannot.

‫فرد البروتين ‪Denaturation of protein‬‬







‫فرد‬









‫مفرود‬

‫إعادة إلى طبيعته‬

Hydrophobic (non-polar R group)

Amino

Hydrophilic (polar R group)

acids

Ionized (charged functional groups)





Peptides Polypeptides Proteins









Primary Secondary Tertiary Quaternary

structure structure structure structure

Single chain H bonds 1- Hydrophobic two or more

of amino acids Interaction polypeptide

Coils & (Van der Waals chains

e.g. Lysozyme Folds interaction);

2- H bonds; e.g. Collagen

e.g. silk 3- Ionic bonds; & Hemoglobin

4- Di-sulfide

bridges;

Lipids;

The Hydrophobic Molecules









1. Fats store large amounts of energy

2. Phospholipids are major components of cell membranes

3. Steroids include cholesterol and certain hormones

1) Fats:

• Lipids are an exception among macromolecules

because they do not have polymers.

• The unifying feature ‫ الصفة المميـٍزة‬of lipids is that they all

َُ

have little or no affinity for water ‫.ال تـَمتزج بالماء‬

– This is because their structures are dominated by non-polar

covalent bonds.



• Lipids are the components ‫ مكونات‬of fats, and are highly

ُ

diverse in form and function.

• Although fats are not polymers, they are large

molecules assembled from ‫ تتكون من‬smaller molecules by

dehydration reactions.

• A fat is constructed from two kinds of smaller

molecules, glycerol and fatty acids ‫.أحماض دُهنية‬

Glycerol H

O H H

Fatty Acid

H H

H C C C H

OH C C C

H C OH H H

Ester link H H H

H C OH

H C OH Dehydration



H



A fat is composed of three fatty acids linked with one glycerol molecule.



Fats are classified into Saturated ‫ مشبع‬and Un-saturated ‫ غير مشبع‬fats



Glycerol consists of a three C skeleton with an OH group attached to each C.



A fatty acid consists of a carboxyl group (COOH) attached to a long

carbon skeleton, often 16 to 18 carbons long.

• The many non-polar C-H bonds in the long hydrocarbon skeleton

make fats hydrophobic.

• In a fat, three fatty acids are joined to glycerol by an ester linkage,

‫ رابطة إستيرية‬creating a triacylglycerol.

• Fatty acids may vary ‫ تختلف‬in length (number of carbons) and in the

number and locations of double bonds.

– If there are no carbon-carbon double bonds, then the molecule is a

saturated fatty acid ‫( مشبع‬has H at every possible position).



•If there are one or more carbon-carbon double bonds, then the

molecule is an unsaturated fatty acid ‫ - حامض دهنى غير مشبع‬formed by the

removal of H atoms from the carbon skeleton.

A)- Saturated Fats ‫الدهون المشبعة‬

The Fatty acid components are saturated (there is no double bonds

between the carbons. All C are linked with H.

Thus, it is saturated with H.



Most animal fats are saturated.

They are solid at room temperature.

Saturated fats-rich diet results in Atherosclerosis ‫.التصلب الشريانى‬







B)- Un-saturated Fats ‫الغير مشبعة‬ ‫الدهون‬

These double bonds are formed by the removal of H atoms.

Most vegetable fats (oils) and fish fats are unsaturated.

They are liquid at room temperature.

They can be synthetically converted to saturated (solid) by adding H

(Hydrogenation ‫.)الهدْ رﭽـَة‬

َ َ

• The major function of fats is energy storage.

– A gram of fat stores more than twice as much energy as a

gram of a polysaccharide.



– Humans and other mammals store fats as long-term

energy reserves ‫ كمخزون طاقة طويل المدى‬in adipose cells ‫.خاليا دهنية‬

2) Phospholipids;

Are major components of cell membranes



• Phospholipids have two fatty acids attached to glycerol and a

phosphate group at the third position.

– The phosphate group carries a negative charge.







• The interaction of

phospholipids with

water is complex.



• The fatty acid tails are

hydrophobic, but the

phosphate group and

its attachments form

a hydrophilic head.

• When phospholipids are added to

water, they self-assemble ‫تتشكل ذاتيا‬

into aggregates ‫ تجمعات‬with the

hydrophobic tails pointing toward

the center and the hydrophilic

heads on the outside.

– This type of structure is called a

micelle ‫.الزهرة‬



• At the surface of a cell

phospholipids are arranged as a

bilayer ‫.طبقة مزدوجة‬

– Again, the hydrophilic heads are on

the outside in contact with the

aqueous solution ‫ المحلول المائى‬and the

hydrophobic tails in the core ‫.المركز‬

– The phospholipid bilayer ‫طبقة مزدوجة‬

forms a barrier ‫ حاجز‬between the cell

and the external environment ‫البيئة‬

‫.الخارجية‬

• They are the major component of cell

membranes.

3) Steroids:

Include cholesterol and certain hormones

• Steroids are lipids with a carbon skeleton consisting of four fused

‫ ملتحمة‬carbon rings.

– Different steroids are created by varying functional groups attached to

the rings.





• Cholesterol, an important

steroid, is a component in

animal cell membranes.





• Cholesterol is also the precursor ‫ المادة الخام‬from which all other

steroids are synthesized.

• Many of these other steroids are hormones, including the sex

hormones.

• While cholesterol is clearly an essential molecule, high levels of

cholesterol in the blood may contribute to Atherosclerosis ‫تصلب الشرايين‬

Fats

(Composed of Lipids)









Saturated Unsaturated Phospholipids Steroids

Animal Fats Vegetable Fats Bi-layer of cell Sex Hormones

membrane & Cholesterol





Hydrogenation

‫هَـدْ رﭽـَــــــــة‬

َ

CHAPTER FUNCTION

THE STRUCTURE AND 5

THE STRUCTURE AND FUNCTION

OF MACROMOLECULES

OF MACROMOLECULES





4- Nucleic Acids:

The Informational Polymers





1. Nucleic acids store and transmit

hereditary information ‫المعلومات الوراثية‬

2. A nucleic acid strand is a polymer

of nucleotides

3. Inheritance is based on

replication of the DNA

double helix

DNA Structure



• DNA is located in the nucleus





• There are two types of nucleic acids

ribonucleic acid (RNA)

And

deoxyribonucleic acid (DNA).

Structures of nucleic acids (DNA & RNA)





3 5 o Phosphate Bases

group

o P o

o DNA Adenine

Base nucleotide

(A)

5 CH2 o Purine

4 H H 1

H

H

Guanine

3 2H (G)

o

Deoxyribose sugar

o P o

o

Base Cytosine

CH2 o (C) Pyrimidine

H H

H

H Thymine

3

5 3 H

(T)

Sugar-phosphate backbone

• The PO4 group of one

nucleotide is attached

to the sugar of the

next nucleotide in line

‫.فى صف مستقيم‬





• The result is a

“backbone” of

alternating ‫تبادل‬

phosphates and

sugars, from which

the bases starts.

Nitrogenous bases ‫القواعد النيتروجينية‬

3 5

Hydrogen bonds







Nitrogenous bases

Cytosine Guanine

(C) (G)



Thymine Adenine

(T) (A)

Uracil (U)

Pyrimidines Purine

5 3

Sugar-phosphate

backbones

DNA

• Adenine (A) would

form 2 hydrogen

bonds only with

thymine (T)





• Guanine (G) would

form 3 hydrogen

bonds only with

cytosine (C).

DNA & RNA

CH2 o CH2 o

H H

H H H

H H

H H

OH

Deoxyribose sugar Ribose sugar

(O on C2 is missed) (no missed O)



Deoxiribo-Nucleic-Acid Ribo-Nucleic-Acid



Double stranded nucleic acid Single stranded nucleic acid



Bases: A, G, C, T Bases: A, G, C, U

The nucleic acid strand is

a polymer of nucleotides



• Nucleic acids are polymers of monomers called nucleotides.



• Each nucleotide consists of three parts: a nitrogen base, a pentose

sugar, and a phosphate group.



• The nitrogen bases (rings of carbon and nitrogen) come in two types:

Purines and Pyrimidines.



• The pentose sugar joined to the nitrogen base is ribose in

nucleotides of RNA and deoxyribose in DNA.



• The only difference between the sugars is the lack ‫ نقص‬of an oxygen

atom on carbon 2 in deoxyribose.

• Polynucleotides are synthesized by connecting the

sugars of one nucleotide to the phosphate of the next

with a phosphodiester link.



• This creates a repeating backbone of sugar-phosphate

units with the nitrogen bases as appendages.



• The sequence of nitrogen bases along a DNA or mRNA

polymer is unique for each gene.



• Genes are normally hundreds to thousands of

nucleotides long.



• The linear order ‫ الترتيب التتابعى‬of bases in a gene specifies

‫ يحدد‬the order of amino acids ‫( ترتيب األحماض األمينية‬the monomers of a

ُ

protein).

Inheritance is based on replication of the DNA double helix



• An RNA molecule is single polynucleotide chain (single strand).

• DNA molecules have two polynucleotide strands (double strand)

that spiral around ‫ تدور حلزونيا‬to form a double helix ‫.حلزون مزدوج‬

• The sugar-phosphate

backbones of the two

polynucleotides are on

the outside of the helix.



• Pairs of nitrogenous

bases (one from each

strand) connect the

polynucleotide chains

with hydrogen bonds.



• Most DNA molecules

have thousands to

millions of base pairs

‫( زوج من القواعد‬bP).

• Because of their shapes, only some bases are compatible ‫متوافقة‬

with each other.

– Adenine (A) always pairs with thymine (T) and guanine (G) with

cytosine (C).



• With these base-pairing rules, if we know the sequence of bases on

one strand, we know the sequence on the opposite ‫ المقابل‬strand.



• The two strands are complementary ‫.مكملين لبعضهما‬

• During preparations for cell division each of the strands serves as

a template ‫ قالب نسخ‬to order nucleotides into a new complementary

strand.



• This results in two identical copies ‫ نسختين طبق األصل‬of the original

double-stranded DNA molecule.

– The copies are then distributed ‫ توزع‬to the daughter cells.



• This mechanism ensures that the genetic information is

transmitted to the new cells.

Repeated Sugar - Phosphate DNA backbone

Sugar–Phosphate-Base One nucleotide

Polynucleotide

DNA Molecule



DNA Double stranded



RNA single stranded



DNA A G C T A T C



mRNA U

T C G A T

U A G

A TOUR OF THE CELL









Panoramic View of the Cell

Cell Theory

1- All organisms are composed of one or

more of cells.





2- Cell is the basic unit of life.





3- The new cell arises only from pre-existing

‫الموجودة‬ cell.

The Cell Cellulae (Small room)





The Organism’s Basic Unit of Structure and Function





Types of cells

‫متقدمة‬

‫بدائية‬

Prokaryotic Eukaryotic





Micro-organisms All other forms

‫الكائنات الدقيقة‬ of life

Prokaryotic and eukaryotic cells

differ in size and complexity





Similarities ‫أوجه ألتشابه‬

• All cells are surrounded by a plasma membrane ‫.غشاء بالزمى‬



• The semi-fluid substance ‫ المادة النصف سائلة‬within the cell is the cytosol,



‫ السيتوبالزم‬containing the cell organelles ‫.عِ ضيات الخلية‬



• All cells contain chromosomes which have genes in the form of DNA.



• All cells also have Ribosomes, tiny organelles ‫ عضيات صغيرة‬that make



proteins using the instructions ‫ التعليمات‬contained in genes.

Prokaryotic and eukaryotic cells

differ in size and complexity





Differences ‫أوجه ألختالف‬

‫إ‬

• A major difference ‫ الفرق األساسى‬between prokaryotic and

eukaryotic cells is the location of chromosomes ‫.موضع الصبغيات‬



– In an eukaryotic cell, chromosomes are contained in a true nucleus (‫.) النواة‬

– In a prokaryotic cell, the DNA is concentrated in the nucleoid (‫)شـبه نواة‬

without a membrane (‫ ) بدون غـشاء‬separating it from the rest of the cell.

– In prokaryotic cell, DNA is a single strand (‫ )أحادى الشريط‬or double strand

(‫ )ثنائى الشريط‬DNA. But in eukaryotic cell, DNA is double strand.

Eukaryotic Cell



Eu: True

Karyon: Nucleus









Animal Cell Plant Cell





What are the functions of cell organelles ?

‫الشبكة اإلندوبالزمية‬ ‫المادة الوراثية‬



‫نوية‬

‫النواة‬

‫الجدار النووى‬



‫سوط حركى‬









‫جسم مركزى‬







‫ريبوسوم‬







‫حلمات دقيقة‬ ‫حهاز جولـﭽـى‬



‫غشاء بالزمى‬



‫ميتوكوندريا‬







‫الهيكل الخلوى‬ ‫جسم محلل‬

‫ُ‬

‫‪The Cell Organelles‬‬

‫عضيــات ألخلي ـ ـ ـ ــة‬

1. The nucleus

- The nucleus contains most of the genes in an eukaryotic cell.

- The nucleus averages about 5 µm in diameter.



• a. Nuclear envelope



Structure:

• The nucleus is separated from the cytoplasm by a

double membrane ‫.غشاء مزدوج‬

• Where the double membranes are fused, a pore ‫ ثقوب‬is

formed

Functions:

• 1. Pores allows macromolecules to pass through.

• 2. The nuclear membrane ‫ الغالف النووى‬is maintaining the

• shape of the nucleus

• b. Chromatin

Structure:

• Within the nucleus, the DNA and associated proteins are

organized into fibrous material, chromatin.



• At the time of division, the chromatin fibers coil up ‫ تلتف‬to be

seen as separate structures, chromosomes.



• Each eukaryotic species has a characteristic number of

َُ

chromosomes ‫.رقم مميـ ٍز من الكروموسومات‬

- A typical human cell has 46 chromosomes (23 pairs), but sex

cells (ovum and sperm) have only 23 chromosomes.



Functions:

1. Chromatin have genes that determine ‫ تحدد‬the general

characters ‫ الصفات العامة‬of organism.



2. The nucleus directs protein synthesis by synthesizing

messenger RNA (mRNA).

– The mRNA travels to the cytoplasm and combines with ribosomes

where the primary structure of a specific protein is formed.

c. Nucleolus

• Nucleolus is a dark region involved in

the production of ribosomes.

2. Ribosomes

• Ribosomes contain ribosomal RNA (rRNA) and protein.

• A ribosome is composed of two subunits ‫ وحدتين‬that combine ‫ تتحد‬to

direct protein synthesis ‫.تخليق البروتين‬









‫حرة‬



‫مرتبطة‬

• In the nucleolus, ribosomal RNA (rRNA) is synthesized

into ribosomal subunits (rRNA + proteins).

• The subunits pass from the nuclear pores to the

cytoplasm where they combine to form ribosomes.

• - Cell types that synthesize large quantities of proteins (e.g.,

pancreas) have large numbers of ribosomes.



• Ribosomes are 2 types:-

1. Free ribosomes are suspended ‫ معلق‬in the cytosol and

synthesize proteins that function within the cytosol.



2. Bound ribosomes are attached to ‫ ملتصق بـ‬the outside of the

endoplasmic reticulum.

– This type of ribosomes synthesize proteins that are either

included into membranes or for secretion outside the cell.

3- The Endomembrane System



a) The endoplasmic reticulum manufacturers membranes

and performs many other biosynthetic functions





b) The Golgi apparatus finishes, sorts, and ships cell

products





c) The Lysosomes are digestive compartments





d) The Vacuoles have diverse functions in cell

maintenance

a)- Endoplasmic reticulum

manufacturers membranes and performs many other

biosynthetic functions



• The ER includes

membranous tubules



• There are two types of ER

that differ in structure and

function.

1. Smooth ER looks smooth

because it lacks ribosomes.

2. Rough ER looks rough ‫خشنة‬

because ribosomes (bound

ribosomes) are attached to

its membranes, including the

outside of the nuclear

envelope.

• The smooth ER:

- It is rich in enzymes and plays a role in metabolic

processes.

- Its enzymes synthesize lipids ‫( دهون‬oils, phospholipids,

and steroids) including the sex hormones ‫.الهرمونات الحنسية‬

- Extensive ‫ توجد بكثرة‬in the liver, it helps detoxify ‫إبطال األثر السام‬

drugs ‫ المخدرات‬and poisons ‫السموم‬



• The rough ER: it contains ribosomes

- is the main site of protein synthesis.

- It is especially abundant ‫ متوفرة‬in those cells that secrete

proteins.

- These secretory proteins are packaged in transport

vesicles that carry them to their next stage.

b)- Golgi apparatus:

finishes, sorts ‫ ,تـُجهز‬packaging and ships ‫ تنقل‬cell products

َ





• Many transport vesicles ‫ أوعية ناقلة‬from the ER travel to the

Golgi apparatus for modification ‫ تطوير‬of their contents.



• The Golgi function is manufacturing ‫ ,تصنيع‬warehousing

‫ ,تغليف‬sorting ‫( تـَجْ هيز‬Packaging), and shipping ‫ نقل‬materials to

outside the cell.

• The Golgi apparatus is extensive specially in secretory

cells ‫.خاليا إفرازية‬



• The Golgi also manufactures polysaccharides.

‫وعاء ناقل‬

c)- Lysosomes ‫األجسام المُحللة‬ are digestive components

• The lysosome is a membrane-bounded sac of enzymes that digests

macromolecules.

• Lysosomal enzymes can hydrolyse proteins, fats,

polysaccharides, and nucleic acids.



• These enzymes work best at pH = 5 (acidic).



• While rupturing ‫ إنفجار‬lysosomes can destroy the cell by

autodigestion (autophagy) ‫.الهضم الذاتى‬



• The lysosomal enzymes and membrane are

synthesized by rough ER and then transferred to ‫تنقل إلى‬

the Golgi then to lysosomes.



• Lysosomes can fuse with food vacuoles ‫ الفحجوة الغذائية‬to

digest food, (when a food item is brought into the cell

by phagocytosis).

• Lysosomes can also fuse with another organelle or

part of the cytosol. This process of autophagy called

recycling which renews the cell

d)- Vacuoles ‫ الفجوات‬have diverse functions ‫وظائف متنوعة‬

in cell maintenance ‫للحفاظ على الخلية‬





• Vesicles ‫ أوعـية‬and vacuoles ‫ فجوات‬are

membrane-bound sacs ‫ أكياس ذات أغشية‬with varied

functions.



1. Food vacuoles ‫ ,فجوة غذائية‬from phagocytosis, fuse with lysosomes.



2. Contractile vacuoles ‫ ,فجوة منقبضة‬found in freshwater protists, pump

excess water out of the cell.



3. Central vacuoles ‫ فجوة مركزية‬are found in many mature plant cells.

Animal cell

Other Membranous Organelles

1)- Peroxisomes (exists in the liver cells):

generate and degrade H2O2 in performing various metabolic functions





• Peroxisomes contain enzymes that transfer hydrogen from various

substrates to oxygen

– An intermediate product of this process

is hydrogen peroxide (H2O2), a poison,

but the peroxisome has another enzyme

that converts H2O2 to water.



– Some peroxisomes break fatty acids down

to smaller molecules that are transported to

mitochondria for fuel ‫.إلنتاج الطاقة‬



– They detoxify alcohol and other harmful

compounds. Thus, it exists extensively in

the liver cells

2- Mitochondrium: is the main energy transformer of cells



• Mitochondria organelles converts energy to forms that cells can

use for work.





• Mitochondria are the sites of cellular respiration, generating ‫تـُنتِج‬

ATP (Adenosine TriPhosphate) from the catabolism ‫ هدم‬of sugars,

fats, and other fuel sources ‫ مصادر طاقة‬in the presence of oxygen.





• Mitochondria are mobile and move around the cell along tracks in

the cytoskeleton.

• Mitochondria have a smooth outer membrane and a highly folded

inner membrane forming cristae ‫.نتوءات‬

• The inner membrane encloses the mitochondrial matrix, a fluid-filled

space with DNA, ribosomes, and enzymes.

The Cytoskeleton ‫الهيكل الخلوى‬

The cytoskeleton is a network of fibers extending throughout ‫ تمتد عبر‬the cytoplasm







Functions:

• The cytoskeleton organizes ‫يرتب‬

the structures and activities of the cell.



• functions in cell motility.

Cytoskeleton





Intermediate

Microtubules Microfilaments filaments

‫أنيبيبات دقيقة‬ ‫ألياف دقيقة‬ ‫ألياف متوسطة‬

Thick Thin Middle

‫سميكة‬ ‫رفيعة‬ ‫متوسطة‬

Responsible for cell Transport Reinforcing the cell

motility, and materials within shape and fixing

separation of the cell. position of

chromosome during organelles.

(Actin protein)

cell division.

(Fibrous protein)

(Tubulin protein)

• The cytoskeleton provides mechanical support and maintains

shape of the cell.



• The cytoskeleton is dynamic, ‫ حركي‬dismantling ‫ يتفكك‬in one part and

reassembling ‫ يتركب‬in another to change cell shape.



• The cytoskeleton also plays a major role in cell motility ‫ حركة الخلية‬by

interacting with motor proteins ‫.البروتين الحركى‬



– In cilia, flagella and muscle cells

motor proteins pull components

of the cytoskeleton past each

other.

• Microtubules functions as tracks ‫ قضيب‬that guide motor proteins

to circulates materials within the cell.



• Motor molecules carry vesicles or organelles to various

destinations ‫ إلى أماكن مختلفة‬inside cell.



• They move chromosomes during cell division

• In many cells, microtubules grow out from a centrosome

‫ الجسم المركزى‬near the nucleus.





• In animal cells, the centrosome has a pair of centrioles,

each with 9 triplets of microtubules ‫تسعة مجموعات كل منها مكون من ثالثة أنيبيبات‬

arranged in a ring ‫.مرتبة دائريا‬

ُ

Cilia and Flagella

• Microtubules are the central structural supports both

cilia ‫ األهداب‬and flagella ‫.األسواط‬

– Both can move unicellular and small multicellular organisms by

propelling water outside the organism.



• Cilia usually occur in large numbers on the cell surface.



• Flagella usually occur in just one or a few per cell.



• Cilia move more like oars ‫ مجاديف‬with alternating power

and recovery strokes.



• Flagella have an undulatory movement ‫.حركة تموجية‬



• So, They differ in their beating pattern ‫.أسلوب الحركة‬

cilia









flagellum

Both cilia and flagella have the same ultrastructure ‫.التركيب الدقيق‬

Both have a core ‫ مركز‬of microtubules sheathed by the plasma

membrane.

Nine doublets (9 + 2 pattern) ‫ تسعة مجموعات كل منها مكون من أنيبيبتان‬of

microtubules arranged around a pair at the center.

Flexible “wheels” of proteins connect outer doublets to each other

and to the core.

The outer doublets

are also connected

by motor proteins.

The structure of cilium

and flagellum is

identical to that of

centriole.

• Cilia and flagella are formed of arms of a motor

protein (dynein ‫.)بروتين الداينين‬



– Addition phosphate group from ATP to dynein and its

removal causes conformation changes in the protein.

– Dynein arms alternately

grab, move, and release

the outer microtubules.

– Protein cross-links limit

sliding and the force is

expressed as bending.

7- Cell membrane



• The plasma

membrane

functions as a

selective barrier

‫ حاجز إختيارى‬that



allows passage

of oxygen,

nutrients, and

wastes for the

whole volume of

the cell.

Cell membrane

Composed of lipids (phospholipids) and proteins

Lipid layer contains hydrophilic and hydrophobic regions





Carbohydrate chains



Hydrophilic ‫مُحب للماء‬





Phospholipid





Hydrophobic ‫كاره للماء‬





Proteins

CHAPTER 5

MEMBRANE STRUCTURE AND

THE STRUCTURE AND FUNCTION OF

MACROMOLECULES

FUNCTION







How things get into and out of the cell

Section A: Membrane Structure

 The plasma membrane separates the living cell from its nonliving

surroundings.

 This thin barrier, 8 nm thick, controls traffic into and out of the cell.

 Like other membranes, the plasma membrane is selectively

permeable, allowing some substances to cross more easily than

others.

 The main macromolecules in membranes are lipids and proteins,

but include some carbohydrates.

 The most abundant lipids are phospholipids.

 Phospholipids and most other membrane constituents are

amphipathic molecules.

Amphipathic molecules have both hydrophobic regions and

hydrophilic regions.

 The phospholipids and proteins in membranes create a fluid

mosaic model.

proteins embedded or attached to a double layer of phospholipids.

 The molecules in the bilayer ‫ طبقة مزدوجة‬are arranged as hydrophobic

fatty acid tails are sheltered ‫ محمية‬from water while the hydrophilic

phosphate groups interact with water.



 Membrane proteins are amphipathic, with

hydrophobic and hydrophilic regions.



 If at the surface, the hydrophilic regions

Fig. 8.1b

would be in contact with water.

 In this fluid mosaic

model, the hydrophilic

regions of proteins and

phospholipids are in

contact with water and

the hydrophobic regions

are in a nonaqueous environment.



Fig. 8.2b

Cell membrane is fluid

• Most of the lipids and some proteins can drift

laterally in the plane of the membrane, but

rarely flip-flop from one layer to the other.

• The lateral movements of phospholipids are

rapid, about 2 µm/second.

• Many larger membrane proteins move more

slowly but do drift.

• As temperatures cool, membranes switch

from a fluid state to a solid state as the

phospholipids are more closely packed.

• Membranes rich in unsaturated fatty acids

are more fluid than those dominated by

saturated fatty acids because the kinks

in the unsaturated fatty acid tails prevent

tight packing.

• To work properly with permeability, membrane must be fluid, about

as fluid as oil.

Membranes are mosaics of structure and function



• A membrane is a collage ‫ تـَجمُّع‬of different proteins embedded

َ

‫ مُـ ْنغمس‬in the fluid matrix of the lipid bilayer.

ِ َ

A)- The plasma membrane has a unique collection ‫ تجمع مميـز‬of proteins.

َ

• There are two populations of membrane proteins.

1. Integral proteins ‫ مُندَمج‬penetrate the hydrophobic core of the lipid

bilayer (transmembrane protein).

2. Peripheral proteins ‫ طرفى‬are not embedded in the lipid bilayer at all.

Instead, they are loosely bounded to the surface of the integral

proteins.



• The integral proteins has a middle

area, hydrophobic regions with

Periphera

nonpolar amino acids. Integral

l proteins

proteins

• And surface area, in contact with the

aqueous environment, they have

hydrophilic regions of amino acids.









Periphera

l proteins

• The proteins in the plasma membrane may provide a variety of major

cell functions.

B)- Membrane carbohydrates are important for cell-cell

recognition



• The membrane plays the key role in cell-cell recognition.

– Cell-cell recognition is the ability of a cell to distinguish one type

of neighboring ‫ المجاورة‬cell from another.

– It is the basis for rejection of foreign cells by the immune system.

– Cells recognize other cells by recognizing the surface molecules,

often carbohydrates, on the plasma membrane.

– Membrane carbohydrates may be covalently bonded either to

lipids, forming glycolipids, or, to proteins, forming glycoproteins.

– The four human blood groups (A, B, AB, and O) differ in the

external carbohydrates on red blood cells.

1- Selective permeability ‫النفاذية اإلختيارية‬

one of the most important functions of cell membrane (Plasma membrane)



 A steady traffic ‫ العبور المنتطم‬of small molecules and ions move across

the plasma membrane in both directions.

 For example, sugars, amino acids, and other nutrients enter a muscle

cell and metabolic waste products leave it.

 The cell absorbs O2 and expels CO2.

 It also regulates concentrations of inorganic ions, like Na+, K+, Ca2+,

and Cl-, by passing them across the membrane.

 However, substances do not move across the membrane barrier

indiscriminately ‫.عشوائيا‬

 Hydrophobic molecules, like hydrocarbons, CO2, and O2, can

dissolve in the lipid bilayer and cross easily.

 Ions and polar molecules, like water, glucose and sugars pass

through with difficulty.

 Proteins can assist and regulate ‫ يساعد و ينظم‬the transport of ions and

polar molecules.

Selective Permeability





CO2

CO2

Nucleus

O2



O2





The cell is able to take up ‫ تـنـتـقى‬particular

molecules and exclude ‫ تـتجنب‬others

2- Passive transport ‫ اإلنتقال السلبى‬is diffusion across a membrane



• Diffusion: ‫اإلنتشار‬

Is the tendency ‫ إستعداد‬of molecules of any substance to spread out ‫ لإلنتشار‬in the

available space randomly ‫.عشوائيا‬

• For example, a permeable membrane ‫ غشاء منفذ‬separating a solution with dye

molecules from pure water, dye molecules will cross the barrier randomly.

• The dye will cross the membrane until both solutions have equal

concentrations of the dye (dynamic equilibrium ‫.)التعادل الديناميكى‬

• A substance will diffuse from where it is more concentrated to where

it is less concentrated, down its concentration gradient ‫.مـُنحدر التركيز‬









• Passive transport: ‫اإلنتقال السلبى‬

is the diffusion of a substance across a biological membrane which

requires no energy.



• The concentration gradient drives diffusion.

Osmosis ‫ : األسموزية‬is the passive transport of water

• Differences in concentration of dissolved materials in two solutions

can lead to the movement of ions from one to the other.

• The solution with the higher concentration of solutes is hypertonic.

• The solution with the lower concentration of solutes is hypotonic.

• Solutions with equal solute concentrations are isotonic.



• Osmosis:

Is a passive transport in which water

diffuses across a selectively permeable

membrane from the hypotonic solution

to the hypertonic solution until the

solutions become isotonic.

Principal of water movement



Osmosis Osmosis

Isotonic





Selectively

permeable

membrane



Low conc. of sugar High conc. of sugar

hypotonic hypertonic

Passive transport of water (Osmosis)

• Hypertonic solution: ‫عالى التركيز‬

contains high concentration of solute ‫ مُذاب‬molecules.

• Hypotonic solution: ‫منخفض التركيز‬

contains low concentration of solute molecules.

• Isotonic solution: ‫متعادل‬

contains equal concentrations of solute molecules







Biological

Membrane





H2O







Hypertonic Hypotonic

Osmoregulation ‫التوازن األسموزى‬



• A cell in a hypotonic solution will

gain ‫ تسحب‬water, swell, and burst.

• The cell in a hypertonic

environment will loose water,

shrivel ‫ ,تنكمش‬and die.

• Organisms without rigid walls

have osmotic problems in either

a hypertonic or hypotonic

environment and must have

adaptations for osmoregulation

to maintain ‫ للحفاظ على‬their internal

environment.

• Example, Paramecium have a

specialized organelle (the

contractile vacuole), that

functions as a pump to force ‫يطرد‬

water out of the cell.

Specific proteins facilitate ‫ تـُسهـِّل‬passive transport

َ



• Many polar molecules and ions diffuse passively through the lipid bilayer

with the help of transport proteins (gated channels ‫.)قنوات م َبوبة‬

ُ

• The passive movement of molecules down its concentration gradient via a

transport protein is called facilitated diffusion.





• Many transport proteins simply provide

channels allowing a specific molecule or

ion to cross the membrane.









• Other transport proteins translocate

‫ ينقل‬the molecules across the

membrane as the protein changes

shape (active transport)

Active Transport ‫النقل النشط‬

Active transport is the pumping ‫ ضخ‬of solutes against their

َ

concentration gradients ‫تزايد التركيز‬



• Some facilitated transport

proteins can move solutes

against their concentration

gradient, from the side where

they are less concentrated to

the side where they are more

concentrated.



• This active transport requires

metabolic energy via ATP.



• Active transport is critical ‫ بالغ األهمية‬for a cell to maintain its internal

concentrations.



• Active transport is performed by specific proteins embedded in

the membranes (transport protein).

1)- Small molecules (Ions )





• The sodium-potassium pump Outside the cell

actively maintains the gradient

of sodium (Na+) and potassium Na

ions (K+) across the membrane. Na Protein

– The animal cell has higher Na molecule

concentrations of K+ and lower Na

concentrations of Na+ inside

the cell.

– The sodium-potassium pump

(T. protein) uses the energy of

one ATP to pump 3 Na+ ions

out and 2 K+ ions in. ATP

Cellular

1ATP T. protein

membrane

Low conc. High conc.

+ 2 of K

+

of K



High conc. Low conc. Inside the cell

of Na

+ 3 of Na+

Adenosine Tri-Phosphate (ATP)

Adenosine



P P P

+ H2O

Triphosphate









Energy P P P



Adenosine Di-Phosphate

Two roles of

membrane protein









Both diffusion and facilitated diffusion are forms of passive transport of molecules

down their concentration gradient, while active transport requires an investment of

energy to move molecules against their concentration gradient.

2)- Large molecules (macromolecules)



Large molecules are transported by Exocytosis and endocytosis





 Small molecules and water enter or leave the cell through the lipid

bilayer or by transport proteins.

 Large molecules, such as polysaccharides and proteins, cross the

membrane by vesicles ‫.أوعية‬



1. Exocytosis ‫:اإلخراج الخلوى‬

a transport vesicle budded from ‫ ينشأ من‬the Golgi apparatus is moved

by the cytoskeleton to the plasma membrane.

When the two membranes come in contact ‫ ,تالمس‬the bilayers fuse

‫ يندمج‬and spill ‫ يُفرع‬the contents to the outside.



2- Endocytosis ‫,اإلدخال الخلوى‬

a cell brings in macromolecules and particulate matter by forming

new vesicles from the plasma membrane and include the

following:

A)- Phagocytosis ‫:اإلبتالع الخلوى‬

Called “cellular eating”. The

cell engulfs ‫ تـَ ْبلَع‬a particle by

extending pseudopodia ‫أقدام‬

‫ كاذبة‬around it and packaging

it ‫ تـُغلفها‬in a large vacuole.



• The contents of the vacuole

are digested when the

vacuole fuses with a

lysosome.

B)- Pinocytosis, ‫الشرب الخلوى‬

“cellular drinking”,

a cell creates a vesicle

around droplets ‫ نقاط‬of

extracellular fluid ‫السائل‬

‫.الموجود خارج الخلية‬

– This is a non-specific

process ‫.عملية غير متخصصة‬

C)- Receptor-mediated endocytosis: ‫اإلدخال الخلوى عن طريق المستقبالت المتخصصة‬









It Is called (Selective eating) which very specific in what substances are

being transported.

• It is triggered ‫ تـُستـَحث‬when extracellular substances bind to special

receptors ‫ ,مُستقبـِالت خاصة‬on the membrane surface. This triggers the

formation of a vesicle ‫وعاء‬

• It enables a cell to take large quantities of specific materials that may

be in low concentrations in the environment.

Transport

Active Passive



Large Small Facilitated Diffusion

molecules Molecules/ions diffusion

(Membrane) (T. protein) (T. protein) (Membrane)









Exocytosis Endocytosis









Pinocytosis Receptor-mediated

Phagocytosis endocytosis

Cellular eating Cellular drinking Selective eating

Using specific

receptors (coated

vesicles) that bind to

specific legends and

engulf it. It is specific

INTRODUCTION

CHAPTER 5

TO

THE STRUCTURE AND FUNCTION

OF MACROMOLECULES

METABOLISM

Section B: Enzymes

1. Enzymes speed up metabolic reactions by lowering energy barriers

2. Enzymes are substrate specific

3. The active site in an enzyme’s catalytic center

4. A cell’s physical and chemical environment affects enzyme activity









Pages 96 - 103

Hydrolysis of sucrose (table sugar)



Dehydration

Glucose + Fructose Sucrose







Hydration (H2O)

Glucose + Fructose

Sucrase

Hydrolysis of sucrose in the presence of Sucrase results

in its two monosaccharide components.



This process include:

1- breaking the bond between Glucose and Fructose;



2- Then, forming new bonds with H+ and OH- from water



This process consumes ‫ تستهلك‬energy (Activation Energy; EA)

Enzymes speed up metabolic reactions by lowering

energy barriers ‫حواجز الطاقة‬



A catalyst ‫ المُحفز‬is a chemical agent that changes the rate of a

reaction without being consumed ‫ دون أن يستهلك‬by the reaction.

ُ

An enzyme is a catalytic protein.

Chemical reactions between molecules involve both bond breaking

and bond forming.

To hydrolyze (hydration) sucrose, the bond between glucose and

fructose must be broken via hydrolysis in the presence of sucrase (the

catalyst).







Sucrase

Enzymes and Activation Energy



Activation Energy: is the amount of energy needed for the

reaction (between enzyme & substrate) to complete (to break the bonds)



Raising the temperature for these reactions to complete

will either denature the compounds or kill the cell.

Thus, organisms must therefore use a catalyst ‫.عامل محفز‬

Catalyst: is a chemical agent that accelerate the reaction

without being consumed by the reaction.



Enzyme is a catalytic protein ‫بروتين مساعد/محفز‬



Enzyme is a specific ‫ متخصص‬catalyst for specific reactants

at any time in the cell (e.g. Sucrase for only Sucrose).

Activation energy: is the amount of energy necessary to push the

reactants over an energy barrier.





At the transition state, the molecules

are at an unstable point.





The difference between free energy

of the products and the free energy

of the reactants is the delta G.



Enzyme speed reactions by

lowering EA. The transition

state can then be reached

even at moderate temperatures.

Enzymes are substrate specific

• The substrate ‫ المادة المطلوب هضمها‬is a reactant which binds to an enzyme.

• When a substrate binds to an enzyme, the enzyme catalyzes ‫ يسهل‬the

conversion ‫ تحويل‬of the substrate to the product ‫.مكوناتها البنائية‬

– Sucrase (catalyst) is an enzyme that binds to sucrose (substrate) and

breaks the disaccharide into fructose and glucose (products).





Enzyme (a catalyst)

Substrate Product (s)



Sucrase

Sucrose + H2O Glucose + Fructose



Specificity of enzyme ‫ تخصصية اإلنزيم‬refers to its Active Site ‫المركز‬

‫ النشط‬which fit to ‫ يـُناسب‬the surface of substrate.

The active site is an enzyme’s catalytic center



The active site of an enzymes is typically a pocket or groove ‫شكل الجيب‬

on the surface of the enzyme into which the substrate fits.

The specificity of an enzyme is due to the fit between the active site

and that of the substrate.

As the substrate binds, the enzyme changes shape to fit the

substrate, bringing chemical groups in position to catalyze the

reaction.









Fig. 6.14

Catalytic Cycle of Enzyme

Active site of enzyme and Catalytic Cycle









Sucrose Sucrase



Glucose







Fructose

H 2O

Catalytic Cycle of Enzyme



1- The substrate binds to the active cite of enzyme.



2- This forms an Enzyme-Substrate complex (via weak

hydrogen bonds).



3- The active cite catalyses the conversion of the

substrate to final products (original components) by

breaking bonds.

4- The resulting products release from the enzyme.



5- The enzyme starts another reaction over and over again.



6- Thus, the enzyme can have a huge metabolic effects in

the catalytic cycle.

A single enzyme molecule can catalyze thousands or more reactions

a second.



Enzymes are unaffected by the reaction and are reusable ‫.يـُعاد استخدامها‬



Most metabolic enzymes ‫ اإلنزيمات األيضية‬can catalyze a reaction in both

the forward and reverse direction.

The actual direction depends on the relative concentrations of products

and reactants.

Enzymes catalyze reactions in the direction of equilibrium ‫.التعادل‬



Enzymes lower activation energy and speed a reaction.



The rate that a specific number of enzymes converts substrates to

products depends in part on substrate concentrations.



At some substrate concentrations, the active sites on all enzymes are

engaged ‫ ,مشغولة‬called enzyme saturation ‫.التشبع اإلنزيمى‬

Cellular factors affecting enzyme activity





• Some conditions lead to the most active conformation and lead to

optimal rate of reaction. These factors are:-









1. Temperature: has a major

impact on reaction rate.

 As temperature increases,

reaction between substrate

and active sites occur faster.

 However, at some point

thermal increase begins to

denature the substrate.

 Each enzyme has an optimal

temperature ‫. درجة حرارة مُثلى‬

Cellular factors affecting enzyme activity



2. pH also influences the reaction rate, each enzyme has

an optimal pH falls between pH 6 - 8 for most

enzymes.

• However, digestive enzymes in the

stomach are designed to work best

at pH 2 while those in the intestine

are optimal at pH 8, both matching

their working environments.



Fig. 6.16b, page 100

3. Cofactors (coenzymes): ‫العوامل المساعدة‬

A non-protein helpers for catalytic activity of enzymes. They bind

permanently ‫ دائما‬to the enzyme and include two types:-

a) Inorganic cofactors, include zinc, iron, and copper.

b) Organic cofactors, include vitamins or molecules derived

from vitamins.

Enzyme inhibitors: ‫مُـثـبِّطات اإلنزيمات‬



They are molecules that prevent enzymes from catalyzing reactions.

– If thy covalently bind with enzyme, inhibition is irreversible ‫.غير منعكس‬

– If binding is weak, inhibition may be reversible ‫.مُنعكس‬

• If the inhibitor binds to the same site as the substrate, then it

called competitive inhibition ‫.تثبيط تنافسى‬









• If the inhibitor binds somewhere

other than the active site, then it

called noncompetitive inhibition.

Types of Inhibitors:



A- Competitive: That resemble the substrate molecule and thus competes

the attach to the active site (blocking the active site).





B- Noncompetitive: They do not compete the substrate directly at the active

site. Rather, they bind with another part of the enzyme resulting in

changing enzyme shape. Finally, deactivate ‫ يـُخمد‬the active site.





Activation and inhibition of enzymes are essential

for metabolic control

The insecticide DDT is inhibitor for key enzymes of nervous system.

Many antibiotics (e.g. Penicillin) inhibits enzymes that help bacteria

to make their cell walls.

CHAPTER 5

THE STRUCTURE AND FUNCTION

Control of Metabolism

The OF MACROMOLECULES



1. Metabolic control often depends on allosteric regulation ‫التحكم الجانبى‬

2. The localization of enzymes within a cell helps order metabolism

The control of metabolism (i.e. enzyme activity)



The cell is controlling its metabolism by regulating enzyme activity:



1)- Allosteric Regulation:

Regulatory molecules that bind weakly to an Alosteric site of the enzyme

(Allosteric Enzymes) in order to inhibit or stimulate the enzyme activity.





A)- Allosteric activator.



B)- Allosteric inhibitor



C)- Feedback inhibition.



2- Cooperativity.

Stabilizes favorable conformational changes at all other

subunits to make enzyme more efficient.

Metabolic control often depends on allosteric regulation



• In many cases, the molecules that naturally

regulate enzyme activity behave like reversible

Allosteric

noncompetitive inhibitors or activators. site

• These molecules often bind weakly to an allosteric

site which is a specific receptor on the enzyme

that is not the active site.

• These molecules can either inhibit or stimulate

enzyme activity.



1)- Allosteric Regulation: ‫التنظيم األلوستيرى‬

• Most allosterically regulated enzymes

are constructed of two or more

polypeptide chains.

• Each subunit has its own active site.

The allosteric sites are often located

where subunits are joined.

• The whole protein exists in two

conformational shapes, one is active,

and one is inactive.

A)- Allosteric activators ‫:منشطات‬

It makes active site functional

(connection of substrate with

enzyme).



B)- Allosteric inhibitors ‫:مثبطات‬

It makes active site non-

functional .





• In many cases, both inhibitors and activators are similar enough in

shape that they compete for the same allosteric sites.

– These molecules may be products and substrates of a metabolic

pathway.

– For example, some catabolic pathways have allosteric sites that are

inhibited when ATP binds, but activated when AMP (adenosine

monophosphate) binds.

– When ATP levels are low, AMP levels are high, and the pathway is turned

on until ATP levels rise, AMP levels fall and inhibition by ATP occurs.

C)- Feedback inhibition

‫:التثبيط باألثر الراجعى‬



It is one of the common

methods of metabolic control

in which a metabolic pathway

is turned off ‫ يتوقف‬by its end

product ‫.الناتج النهائى‬



• Example:

the production of Isoleucine

from Thereonine by

Thereonine deaminase:-



• The end product acts as an

inhibitor of an enzyme in the

pathway.



• When the product is

abundant ‫ ,متوفر‬the pathway is

turned off, when rare ‫ قليل‬the

pathway is active.

2)- Cooperativity regulation ‫التنظيم التضامنى‬



• It occurs In enzymes with

multiple catalytic subunits,

binding by a substrate to

one active site stabilizes

favorable conformational

changes at all other

subunits, a process called

cooperativity ‫.التضامنية‬





• This mechanism amplifies ‫ يـُزيد‬the response ‫ استجابة‬of

enzymes to substrates, making the enzyme to accept

additional ‫ إضافى‬substrates.

The localization of enzymes within a cell ‫ وضع اإلنزيمات بالخلية‬helps

order metabolism ‫تنظيم األيض‬



• Some enzymes and enzyme complexes have fixed locations ‫موضع ثابت‬

within the cells as structural components of particular membranes.



• Others are confined

within membrane-

enclosed organelles

• (lysosomes and mitochondria).



• Both methods concentrate

enzymes for efficiency.

‫لزيادة الفاعلية‬

Respiration



Alveoli



External respiration









‫الــدم‬

Internal respiration



‫خاليا‬

Cellular respiration ‫الجـسـم‬

CELLULAR RESPIRATION:

HARVESTING CHEMICAL ENERGY







Section A: The Principles of Energy Harvest

Section A: The Principles of Energy Harvest



1. Cells recycle the ATP they use for work



2. Redox reactions ‫ تفاعالت األكسدة-اإلختزال‬release energy when

electrons move closer to electronegative atoms



3. Electrons “fall” ‫ تنتقل‬from organic molecules to oxygen

during cellular respiration



4. The “fall” of electrons during respiration is stepwise ‫,مرْ حلى‬

َ َ

via NAD+ and an Electron Transport Chain

Respiration

Cellular Respiration



O2 H2O

Food

(Fuel of energy)

Respiration Energy

+

O2 CO2







Cellular Activities





Organic compounds + O2 Energy + CO2 + H2O

1. Cells recycle the ATP they use for work

• ATP (Adenosine Tri-Phosphate) is the important

molecule in cellular energetics ‫.عمليات إنتاج الطاقة‬



– The attachment of three negatively-charged phosphate groups

(P) is an unstable ‫ ,غير مستقر‬energy-storing ‫ مخزن للطاقة‬arrangement.



– Loss of the end phosphate group release energy





• The price of most cellular work is the conversion of

ATP to ADP and phosphate (P).

• An animal cell regenerates ‫ تعيد إنتاج‬ATP from ADP by

adding P via the catabolism ‫ هدم‬of organic molecules.

Adenosine Tri-Phosphate (ATP)

Adenosine



P P P

+ H2O

Triphosphate









Energy P P P



Adenosine Di-Phosphate

The transfer of the terminal phosphate group from ATP to

another molecule is phosphorylation ‫.فـَسْ ـفـَرة‬



This changes the shape

of the receiving molecule

in order to work

(transport, mechanical,

or chemical).



When the phosphate

groups leaves the

molecule, the

molecule returns to

its original shape (stop).

How dose ATP drive cellular work ?



P P P





Organelle







Motor P

Protein

Microtubule

Energy

2. Redox reactions release energy when electrons move

closer to electronegative atoms



• Catabolic pathways relocate ‫ يبدل أماكن‬the electrons stored in food

molecules, releasing energy that is used to synthesize ‫ لتخليق‬ATP.

• Oxidation-reduction reactions (Redox reactions):

Are reactions that result in the transfer of one or more electrons

from one reactant to another

• Oxidation:

Redox reactions require

Is the loss ‫ فقـد‬of electrons.

• Reduction: both a donor and acceptor of e.

Is the addition ‫ إكتساب‬of electrons.





+

X e- + Y X + Y

Oxidation Reduction



Na + Cl Na+ + Cl- Energy

3. Electrons “fall” from organic molecules to oxygen

during cellular respiration



• In cellular respiration, glucose and other fuel molecules are oxidized, releasing

energy.



e -



C6H12O6 + 6O2 6CO2 + 6H2O + (ATP + Heat)

Reducing Oxidizing Energy = 686 kcal/mol

agent agent Energy



• Glucose is oxidized, oxygen is reduced, and electrons loose potential energy.

• H is the source of electrons that transfere to O.

• Thus, molecules that have an abundance of ‫ وفرة من‬hydrogen are excellent fuels

because their bonds are a source of electrons that “fall” closer to oxygen.

• Enzymes lower the barrier of activation energy, allowing these fuels to be

oxidized slowly.

• The resulting energy is used by the cell to synthesis ATP .

4. The “fall” of electrons ‫ اإلنحدار اإلليكترونى‬during respiration is

stepwise ‫ ,مرحلى‬by NAD+ and an electron transport chain





• Cellular respiration does not oxidize glucose in a single step that

transfers all the hydrogen in glucose to oxygen at one time.



• Rather, glucose and other fuels are broken down gradually ‫ تدريجيا‬in

a series of steps, each catalyzed by a specific enzyme.



• At key steps ‫ ,فى الخطوات األساسية‬hydrogen atoms move from glucose

and passed first to the coenzyme NAD+ (Nicotinamide Adenine

Dinucleotide).



• Dehydrogenase enzymes strip two hydrogen atoms from the fuel

(e.g., glucose), pass two electrons to NAD+ and release H+.



Dehydrogenase

H-C-OH + NAD+ C=O + NADH + H+

• This changes the oxidized form, NAD+, to the reduced form

NADH.



• NAD + functions as the oxidizing agent in many of the redox steps

during the catabolism of glucose.









As electrons “fall” from NADH to oxygen,

Their energy is tapped to synthesize ATP.

• Cellular respiration uses an electron transport chain ‫سلسلة نقل اإلليكترونات‬

to break ‫ يـُقـَسم‬the fall of electrons to O2 into several steps ‫.عدة خطوات‬



• The electron transport chain, consisting

of several molecules (primarily proteins),

is built into the inner membrane of a

mitochondrion.



• NADH takes electrons from food at the

“top” of the chain.

• At the “bottom”, oxygen captures the

electrons and H+ to form water.



• The free energy change from “top” to

“bottom” is -53 kcal/mole of NADH.

• Electrons are passed by increasingly

electronegative molecules in the chain

until they are caught by oxygen (the

most electronegative).

Summary of electron “Fall” steps during respiration

- Falling of all H atoms from glucose to O is gradually not at once.



- It occurs in steps, each one is catalyzed by an enzyme.



- H atoms of glucose pass first to the co-enzyme NAD+ to form NADH



- Then from NADH to electron transport chain, and finally to O and

releases energy to form ATP.







Mitochondrion

NAD+ e e

Food H NADH Transport chain Oxygen



Energy

ATP ADP

CELLULAR RESPIRATION:

HARVESTING CHEMICAL ENERGY









Section B:

The Process of Cellular

Respiration

1. Respiration involves glycolysis, the Krebs cycle, and

electron transport

2. Glycolysis (in cytoplasm): harvests chemical energy by

oxidizing glucose (breaking glucose into 2 molecules of

pyruvate).

3. The Krebs cycle (in motochonderial matrix): completes the

energy harvest by oxidizing the organic molecules.

4. The electron transport chain (inner mitochondrial

membrane): to synthesis ATP.



Cellular respiration generates 38 ATP molecules

for each sugar molecule it oxidizes.

Summary of Glycolysis (Splitting of glucose)





It is the process of breaking a glucose into 2 Pyruvate.



It is a source for some ATP & NADH and occurs in the

CYTOSOL (cytoplasm).





It has two phases

A)- Energy investment phase

1)- Glucose is phosphorylated twice by adding 2 P

coming from 2 ATP (substrate-level-phosphorylation).



2)- Thus, Glucose (6-C) splits into two small sugar

molecules (each with 3-C).

Summary of Glycolysis (Splitting of glucose)





B)- Energy pay-off phase



3)- The two resulting 3-C-sugars are then oxidized (losing e- (H)).

4)- The resulting e- from the two 3-C-sugar are used for reducing 2

NAD+ into 2 NADH molecules via dehydrogenase.



5)- 4 ATP are formed by adding 4P to 4ADP molecules.



6)- The net yield of this process is the formation of 2 NADH,

2 ATP and 2 pyruvate molecules.

7)- Now pyruvate is ready for Krebs Cycle.

2. The Krebs cycle completes the energy harvest by

oxidizing organic molecules (in mitochondrial matrix):



• If O2 is present, pyruvate enters the mitochondrion where enzymes of

the Krebs cycle complete the oxidation of this organic fuel to CO2.



• As pyruvate enters the mitochondrion which modifies pyruvate

to acetyl-CoA which enters the Krebs cycle in the matrix.

– A carboxyl group is removed as CO2.

– A pair of electrons is

transferred from the

remaining two-carbon

fragment to NAD+ to form

NADH.

– The oxidized fragment,

acetate, combines with

coenzyme A to form

acetyl-CoA.

Summary of Respiration



- Glycolysis occurs in the cytosol and breaks glucose into 2 pyruvates



- Krebs Cycle takes place within the mitochondrial matrix, and breaks

a pyruvate into CO2 and produce some ATP and NADH.

- Some of ATP is produced at these tow steps via (substrate-level-

phosphorylation).

- Electron Transport Chain accepts e- from NADH and passes these e-

from one protein molecule to another.

- At the end of the chain, e- combine with both H+ and O2 to form H2O

and release energy.

- These energy are used by mitochondria to synthesis 90% of the cellular

ATP via ATP-synthase, a process called Oxidative Phosphorylation, in

the inner membrane of mitochondria.

Summary of cell respiration

CHEMICAL SIGNALS IN ANIMALS









Egg Larva Pupa Adult

Introduction

• Nervous and endocrine systems are the main internal

communication and regulation systems.



• The animal hormone-secreting cells constitute the endocrine

system.



• Hormone secreting organs are called endocrine glands (ductless

glands).



• Hormone is a chemical signal secreted into blood stream and

regulates communicating messages within the body.



• Target cell is the site that reached by the hormone to which it

responds.



• Complete changes in the body is regulated by hormones (e.g.

metamorphosis in insects).



• Types of hormones are [ Polypeptide H., Steroid H. or Amino acid

derivatives H ].

• Many endocrine organs contain specialized nerve cells called

neurosecretory cells that secret hormones.



• The hormone epinephrine has two functions:

– As a hormone of the endocrine system.

– As a signal in the nervous system.





• Feedback is common in regulation the activity of both endocrine

and nervous systems (homeostasis) (Fig. 45.1, page 956):

– Calcitonin and parathyroid hormones play an important role in

maintaining the concentration of the blood calcium constant.

– They are secreted from thyroid and parathyroid glands respictively.





• Hormones regulate the development of

invertebrates (e.g. insects)

A variety of local regulators affect neighboring target cells





• Growth factors:

Are proteins and polypeptides that stimulate cell proliferation

• Example: nerve growth factor (NGF) affects certain embryonic cells,

developing white blood cells, and other kinds of cells.





• Nitric oxide (NO):

– Though a gas, NO is an important local regulator.

– When secreted by neurons, it acts as a neurotransmitter.

– When secreted by white blood cells, it kills bacteria and cancer cells.

– And when secreted by endothelial cells, it dilates the walls of blood

vessels.





• Prostaglandins (PGs): modified fatty acids.

– PGs secreted by the placenta stimulate uterine contractions during

childbirth.

– Other PGs play a role in inflammation and the blood flow to the lungs.

Most chemical signals bind to plasma-membrane proteins,

initiating signal-transduction pathways.





Mechanism of chemical signaling:



The chemical signals secreted by a cell either:

a): Bind to a receptor protein on the surface of the target cell. This will

trigger signal transduction pathway. For example protein hormones.

a): Penetrate the cell and bind to a receptor protein inside the target cell.

This also will trigger signal transduction pathway (e.g. steroid hormones

for synthesizing a specific protein).

Steroid hormones, thyroid hormones, and some local regulators enter

target cells and bind to intracellular receptors









• Estrogen, progesterone, vitamin D and NO.

– Usually, the intracellular receptor activated by a hormone is a

transcription factor.





• Ecdysone (insect molting hormone).

– A steroid hormone triggers the special cells to secrete new

exoskeleton.

• Different signal-transduction pathways in different cells can lead

to different responses to the same signal.

The Vertebrate Endocrine System

‫الصنوبرية‬

 Tropic hormones ‫المنبه للغدد‬ ‫النخامية‬



target other endocrine ‫الدرقية‬



glands and are

important to understanding

chemical coordination. ‫الكظرية‬





• Humans have nine

endocrine glands.









Fig. 45.5, Page 960

The hypothalamus and pituitary integrate many

functions of the vertebrate endocrine system



• The hypothalamus integrates endocrine and

nervous function.

– Neurosecretory cells of the hypothalamus produce

hormones.



a) Releasing hormones stimulate the anterior pituitary

(adenohypophysis) to secrete hormones.



b) Inhibiting hormones prevent the anterior pituitary from

secreting hormones.





1)- Pituitary gland: secrets 9 hormones ( 7 hormones by the

anterior part and 2 hormones by the posterior part).

A)- Anterior pituitary hormones.

1) Growth hormone (GH): a protein.

• Stimulates growth and metabolism.

• Secretion regulated by hypothalamic hormones.

• Acts directly on tissues or acts via growth factors.

• Gigantism: ‫ العملقة‬excessive GH during development.

• Acromegaly: excessive GH production during adulthood.

• Hypopituitary dwarfism ‫ :القزمية‬childhood GH deficiency.

2) Prolactin (PRL): a protein.

• Stimulates milk production and secretion.

• Secretion regulated by hypothalamic hormones.

3) Gonadotropins: glyocoproteins.

• Follicle-stimulating hormone (FSH).

– Stimulates production of sperm and ova.

– Secretion regulated by hypothalamic hormones.

• Luteinizing hormone (LH) ‫.المحفز لتكوين الجسم األصفر‬

ُ

– Stimulates ovaries and testes.

– Secretion regulated by hypothalamic hormones.

4) Thyroid-stimulating hormone (TSH): a glycoprotein.

• Stimulates thyroid gland.

• Secretion regulated by thyroxine in blood.

• Secretion regulated by hypothalamic hormones.





5) Adrenocorticotropic hormone (ACTH): a peptide

• Stimulates adrenal cortex secretion of glucocorticoids

• Secretion regulated by glucocorticoids and hypothalamic

hormones.





6) Melanocyte-stimulating hormone (MSH): a peptide.

• May play a role in fat metabolism.





7) Endorphins: peptides.

• Inhibit pain perception.

• Effects mimicked by heroin and other opiate drugs.

The anterior pituitary gland hormones









Melanocyte-

stimulating H.









Adrenocorticotropic









Also called gonadotropine

hormones ‫هرمونات المناسل‬

B)- Posterior pituitary hormones.

– Oxytocin: a peptide.

• Stimulates contraction of the uterus and mammary glands.

• Secretion regulated by the nervous system.

– Antidiuretic hormone (ADH): ‫ مضاد إلدرار البول‬a peptide.

ُ

• Promotes retention of water by the kidneys.

• High level decreases urination and vice versa.

• Secretion regulated by water/salt balance.







2- Pineal gland: ‫الغدة الصنوبرية‬

is a small mass of tissue near the center of the mammalian brain

and involved in biorhythms.



– The pineal gland secretes the hormone, melatonin, an amine.

• Involved in biological rhythms associated with reproduction.

• Secretion regulated by light/dark cycles.

 Posterior pituitary

(neurohypophysis)

stores and secretes

hormones produced

by the hypothalamus.









Antidiuretic H

3. Thyroid gland: secrets hormones function in development,

bioenergetics, and homeostasis ‫ثبات البيئة الفسيولوﭽـية الداخلية‬



• The thyroid gland of mammals consists

of two lobes located on the ventral

surface of the trachea. It contains 4

small Parathyroid glands. It plays role in

maintaining normal blood pressure, Thyroid

heart rate digestion ..etc. releasing H.



• Thyroid glands secretes 3

hormones:

I. Tri-iodothyronine [(T3), 3 I

atoms]: amino acid derivative.

Thyroid

stimulating H.

II. Thyroxine [(T4), 4 I atoms]:

amino acid derivative.

– Stimulates and maintain metabolic

processes.

– Secretion regulated by TSH

hormones.

III. Calcitonin: a peptide.

 Lowers blood Ca2+ levels.

 Its secretion regulated by calcium in blood.







a) Hyperthyroidism: the excessive secretion of thyroid

hormones causes:

• high body temperature

• sweating

• weight loss

• Irritability

• high blood pressure.



b) Hypothyroidism: an insufficient ‫ قليل‬amount of thyroid

hormones because deficiency of I in human diet (causes Goiter).

 Infants: cretinism.

 Adults: weight gain, lethargy, cold intolerance.

 Goiter ‫ :تضخم الغدة‬often associated with iodine deficiency ‫.نقص‬

Parathyroid gland: Parathyroid hormone (PTH): a peptide

• PTH is secreted by The four parathyroid glands which embedded

in the surface of the thyroid gland. It functions as:

– Raises blood Ca2+ levels.

– Secretion regulated by calcium in the blood.

– Causes osteoclasts ‫ فقد الكالسيوم‬to break down bone, releasing Ca2+ into

the blood.

– Stimulates the kidneys to reabsorb ‫ تعيد إمتصاص‬Ca2+.

– Stimulates kidneys to convert vitamin D to its active form, which

stimulate intestine to absorb Ca2+.

– PTH and calcitonin are antagonistic ‫ متضادين‬hormones. Thus PTH and

calcitonin regulate blood calcium level (important role in homeostasis).



• Hypoparathyoidism (tetany): it is a lack of PTH which causes:

– Ca2+ levels in the blood drop.

– Convulsive contractions of the skeletal muscles.

Hormonal control of Ca2+ homeostasis in mammals blood

5. Pancreas: Endocrine tissues of the pancreas secrete insulin and

glucagon, antagonistic hormones that regulate blood glucose



• The pancreas has both endocrine and exocrine functions.

– Exocrine function: secretion of bicarbonate ions and digestive

enzymes.

– Endocrine function: insulin and glucagon secreted by beta and alpha

cells of islets of Langerhans ‫.جيوب النجرانز‬



1. Insulin: a protein secreted by beta cells.

• Lowers blood glucose levels.

– Stimulates all body cells (except brain cells) to take up glucose.

– Slows glycogenolysis ‫( يبطىء تحلل الجليكوجين‬a source of glucose).

– Inhibits gluconeogenesis ‫.يوقف تكوين الجلوكوز‬

• Secretion regulated by glucose in blood (negative feedback).



– Hypoinsulinism: diabetes mellitus ‫.نقص اإلنسولين‬

• Hereditary factors ‫ عامل وراثى‬and play a role in its development.

• High blood sugar levels – sugar excreted in the urine.

• Symptoms: excessive urination ‫ كثرة التبول‬and excessive thirst ‫.العطش‬

a) Type I diabetes mellitus (insulin-dependent diabetes).

• Autoimmune disorder.

• Usually appears in childhood ‫.الطفولة‬

• Treatment: insulin injections.



b) Type II diabetes mellitus (non-insulin-dependent diabetes).

• Usually due to target cells having a decreased responsiveness to

insulin ‫.قلة اإلستجابة لإلنسولين‬

• Usually occurs after age 40 – risk increases with age.

• Accounts for over 90% of diabetes cases.



2. Glucagon: a protein secreted by alpha cells.

• Raises blood glucose levels.

– Stimulates glycogenolysis ‫ تحلل الجليكوجين‬in the liver and skeletal

muscle to produce glucose.

– Secretion regulated by glucose in blood (negative feedback).

6. The adrenal gland: adrenal medulla and adrenal cortex help

the body manage stress



• The adrenal glands are located adjacent to the kidneys.

– The adrenal cortex ‫ القشرة‬is the outer portion.

– The adrenal medulla is the inner portion.



I- Adrenal medulla ‫.المركز‬

– Developmentally and functionally related to the nervous system.

– It produces the following hormones (in response to stress):



a) Epinephrine (adrenaline ‫.)هرمون القلب‬

b) Norepinephrine (noradrenaline).

They are amino acid derivatives (synthesized from tyrosine)

and function as:

• Raises blood glucose level and blood fatty acid level.

• Increases heart rate and stroke volume and dilates bronchioles.

• Shunts blood away from skin, digestive organs, and kidneys,

and increases blood flow to heart, brain, and skeletal muscle.

II- Adrenal cortex: reacts to stress.

• Secretion of corticosteroids (a family of steroid hormones) is

regulated by the nervous system in response to stress for example:



a) Glucocorticoids.

• Raises blood glucose level.

• Secretion regulated by ACTH (Adrenocorticotropic hormone).

• Abnormally high doses are administered as medication to

suppress the inflammation response.



b) Mineralocorticoids (example: aldosterone, which affects salt and

water balance).

• Promotes re-absorption of Na+ and excretion of K+ in kidneys.

• Their secretion regulated by K+ in blood.



– A third group of corticosteriods are Sex hormones.

• Androgens secreted by the adrenal cortex may account for the female

sex drive.

• The adrenal cortex also secretes small amounts of estrogens and

progesterone.

7. Tests and ovaries: Gonadal steroids regulate growth,

development, reproductive cycles, and sexual behavior



a) Testes hormones:

– Testosterone: steroids.

• Supports sperm formation.

• Promote development and maintenance of male sex characteristics.

• Secretion regulated by FSH and LH.





b) Ovaries hormones:

1) Estrogens: steroids.

• Stimulate uterine lining growth.

• Promote development and maintenance of female sex

characteristics.

• Secretion regulated by FSH and LH.

2) Progesterone: steroids.

• Promotes uterine lining growth.

• Secretion regulated by FSH and LH.

8- Thymus gland:



Secretes Thymosin: a peptide.

It stimulates T lymphocytes.







Protein hormones affect target cells via

receptors on the membrane protein



Steroid hormones inter the target cells

and trigger protein synthesis via

receptors in the nucleus.

MENDEL AND THE GENE IDEA





Section A: Gregor Mendel’s Discoveries

Mendel brought an experimental and quantitative approach

to genetics



• Around 1857, Mendel began breeding

garden peas to study inheritance ‫.وراثة‬

Because they are available in many

varieties with distinct heritable ‫مُتوارث‬

characters ‫ صفات‬with different traits

(genes).



• Each pea plant has male (stamens)

and female (carpal) sexual organs.

• In nature, pea plants typically

self-fertilize ‫ ,تلقيح ذاتى‬fertilizing ova

with their own pollens.

• However, Mendel could also move

pollens ‫ حبوب اللقاح‬from one plant to

another to cross-pollinate ‫ يُـلقح‬plants.

• In a breeding experiment, Mendel would cross-pollinate

‫( تلقيح خلطى‬hybridize ‫ )هجن‬two contrasting ‫ ,متباينين‬true-

َ

breeding pea varieties ‫.أنواع‬

– The true-breeding parents are the P (Parental generation) and

their hybrid offspring ‫ النسل المُهجن‬are the F1 (1st Filial generation) .





• Mendel would then allow the F1 (1st Filial generation) hybrids

to self-pollinate to produce an F2 generation.



• It was mainly Mendel’s quantitative analysis ‫ تحليل كمى‬of F2

plants that revealed the two fundamental lows of

heredity:



A)- The law of segregation.

B)- The law of independent assortment.

A)- Law of segregation: )‫ )قانون اإلنعزال‬the two alleles ‫ ﭽـينات‬for a

character are isolated into separate gametes



• The F1 hybrids from a cross ‫تلقيح‬

between purple-flowered and white-

flowered pea plants would have pale

purple flowers ‫.بنفسجى باهت‬



• Instead, ‫ ولكن‬the F1 hybrids all have

purple flowers, just a purple like their

parents.



• This cross produced a 3 purple to 1

white ratio of traits in the F2 offspring,



• Mendel reasoned that the heritable

factor for white flowers was present

in the F1 plants, but it did not affect

flower color.



• Thus, purple flower is a dominant color

)‫ (صفة سائدة‬and white flower is a recessive

color )‫.(صفة مُتنحية‬

• Mendel found similar 3 to 1 ratios of two traits among

F2 offspring when he conducted crosses for six other

characters, each represented by two different varieties

‫.صفتين مختلفتين‬





• For example, when Mendel crossed two true-breeding

varieties, one of which produced round seeds ‫,بذور مُستديرة‬

the other of which produced wrinkled seeds ‫ ,بذور مُجعدة‬all

َ

the F1 offspring had round seeds, but among the F2

plants, 75% of the seeds were round and 25% were

wrinkled (see second low in the next lecture).

• Mendel developed a hypothesis ‫ إفتراض‬to explain these results that

consisted of four related ideas.



1. Alternative version of genes (different alleles ‫ )الـﭽينين المتقابلين‬account

for variations in inherited characters.

– Different alleles vary somewhat in

the sequence of nucleotides at

the specific locus ‫ موضع‬of a gene.



2. For each character, an organism

inherits ‫ يرث‬two alleles, one from

each parent.

– These homologous loci ‫موقعُه على الكروموسوم‬

ِ َ

may be differ

– In the flower-color example, the F1 plants

inherited a purple-flower allele from one

parent and a white-flower allele from the

other.

3. If two alleles differ, then, the dominant allele is fully expressed in

the organism’s appearance and the recessive allele has no effect

on the organism’s appearance.





4. The two alleles for each character segregate (separate) ‫ينفصل‬

during gamete production.



– This segregation of alleles because of the distribution of homologous

chromosomes to different gametes in meiosis.

– If an organism has identical allele for a particular character, then that

allele exists as a single copy in all gametes.

– If different alleles are present, then 50% of the gametes will receive one

allele and 50% will receive the other.





• The separation of alleles into separate gametes

is summarized as Mendel’s law of segregation.

Summary

Mendelian inheritance reflects rules of probability for the

behaviour of genes.

For each character, an organism inherit two alleles (one from each

parent).



Red colour

gene (allele)

Homologous

chromosomes

White colour

gene (allele)



If the two alleles differ, one of them will be Dominant, and the other

is Recessive.



The two alleles (genes) for a character are separated (segregated)

into separate gametes and aggregated again by fertilization.

• Mendel’s law of segregation accounts

for the 3:1 ratio in the F2 generation.



• The F1 hybrids will produce two

classes of gametes, half with the

purple-flower allele and half with the

white-flower allele.



• During self-pollination, the gametes

of these two classes unite randomly.

• This can produce four equally likely

combinations of sperm and ovum.



• A Punnett square predicts the results

of a genetic cross between individuals

of known genotype‫.الطرز الـﭽينى‬



• A Punnett square analysis of the

flower-color example demonstrates

Mendel’s model.

• Mendel’s model accounts for the 3:1

ratio in the F2 generation

Pea plant

PP X pp Pp X Pp



P p P p

P p







Dominant Recessive

allele Pp allele PP Pp Pp pp

100% Purple

3 Purple : 1 White

Homozygous Heterozygous



F1 generation F2 generation

Phenotype:

Phenotype Is the organism’s appearance ‫.المظهر‬

(Colour)

Genotype:

Is the organism’s genetic makeup

‫.الطرز الـﭽينى‬





PP PP Homozygous pp

An organism having a pair of

identical alleles



Genotype Pp Heterozygous

(Genetic make up)

An organism having a pair of two

different alleles

• Dominant character (allele) ‫الصفة السائدة‬

Is fully expressed in the organism’s appearance.

• Recessive character (allele) ‫الصفة المُتنحية‬

Has no noticeable effect ‫ تأثير غير ملحوظ‬on the organism’s appearance.

• Homozygous ‫متماثل الجينات‬

ُ

An organism with two identical alleles for a character.

• Heterozygous ‫مختلف الجينات‬

ُ

An organism with two different alleles for a character.

• Karyotype ‫الطرز الكروموسومى‬

The display of an organism’s chromosomal pattern

• Phenotype ‫الطرز المظهرى‬

A description of an organism’s traits (feature ‫.)مظهر‬

• Genotype ‫الطرز الجينى‬

A description of an organism’s genetic makeup.

• For flower color in peas, both PP and Pp plants have

the same phenotype (purple) but different genotypes

(homozygous and heterozygous).



• The only way to

produce a white

phenotype is to

be homozygous

recessive (pp)

for the flower-

color gene.

• It is not possible to predict the genotype of an

organism with a dominant phenotype.

– The organism must have one dominant allele, but it could be

homozygous dominant or heterozygous.





• A test cross, breeding a

homozygous recessive

with dominant phenotype,

but unknown genotype,

can determine the identity

of the unknown allele.



Q: What is the result of

Cross hybridization of

purple X white colored

flowers ?

MENDEL AND THE GENE IDEA





Section C: Mendelian Inheritance in Humans

2- The law of Independent Assortment: ‫التوزيع الحر للـﭽـينات‬

each pair of alleles segregates into gametes independently





• Mendel’s experiments that followed the inheritance of flower color or

other characters focused on only a single character via monohybrid

crosses ‫.التزاوج أحادى الصفة‬



• He conduced other experiments in which he followed the inheritance

of two different characters (a dihybrid cross ‫.)التزاوج ثنائى الصفة‬



• In one dihybrid cross experiment, Mendel studied the inheritance of

seed color and seed shape.

– The allele for yellow seeds (Y) is dominant to the allele for green

seeds (y).

– The allele for round seeds (R) is dominant to the allele for wrinkled seeds

(r)



• Mendel crossed true-breeding plants that had yellow & round seeds

(YYRR) with true-breeding plants that has green & wrinkled seeds

(yyrr).

• The two pairs of alleles segregate independently of each other.

– The presence of one specific allele for one trait has no impact ‫ تأثير‬on

the presence of a specific allele for the second trait.





• When sperm and ova each with

four classes of alleles

combine, there would be 16

equally probable ways in which

the alleles can combine

in the F2 generation.

• These combinations produce

four distinct phenotypes in a

9:3:3:1 ratio.

• This was consistent with

Mendel’s results.

• Each character appeared to be

inherited independently.

Mendel’s low of Independent (Dihybrid cross)

It is a mating between two parent plants differing in two characters.





YY RR X yy r r

Y

R

YR y r



y

Y y Rr

r

F1 Yellow Round

Yy Rr X Yy Rr



YR Yr yR yr



YR YYRR

Yellow Round



Yr YYrr

Yellow Wrinkled



yR yyRR

Green Round



yr yyrr

Green Wrinkled









F2: % of Phenotype ?

Many human disorders ‫ أمراض‬follow Mendelian

patterns of inheritance

• Thousands of genetic disorders ‫ ,أمراض وراثية‬including disabling ‫ اإلعاقة‬or

deadly hereditary diseases ‫ ,األمراض الوراثية المُميتة‬are inherited as simple

recessive traits ‫.صفات وراثية مُتنحية‬

• These range from the relatively mild (albinism ‫ )األلبينو، البُهاق‬to life-threatening

(cystic fibrosis).

• Heterozygotes have a normal phenotype because one “normal” allele

produces enough of the required factors (for normal trait).

• A recessively inherited disorder shows up ‫ يظهر‬only in the

individuals who inherit homozygous recessive allele from parents.

• Thus, individuals who lack the disorder are either homozgyous dominant

or heterozygous.

• Heterozygous member may have no clear phenotypic effects, but is a

carrier who may transmit a recessive allele to their offspring.

• Most people with recessive disorders are born from carrier parents with

normal phenotypes.

– Two carriers have a 1/4 chance of having a child with the disorder, 1/2 chance of

a carrier, and 1/4 free.

A- Recessively inherited disorders ‫الصفات المرضية المتنحية‬

1. Cystic fibrosis: a lethal recessive disorder

– One in 25 person is a carrier.

– The normal allele codes for a membrane protein that transports

Cl- between cells and the environment.

– If these channels are absent, there are abnormally high

extracellular levels of chloride that causes the mucus coats of

certain cells to become thicker ‫ سميكة‬and stickier ‫ لزجة‬than normal.

– This mucus build-up in the pancreas, lungs, digestive tract, and

elsewhere favors bacterial infections.

– Without treatment, affected children die before five, but with

treatment can live past their late 20’s.





2. Tay-Sachs disease a lethal recessive disorder.

– It is caused by a dysfunctional enzyme ‫ إنزيم غير عامل‬that fails to break

down specific brain lipids.

– The symptoms begin with seizures ‫ ,حول‬blindness, and degeneration

of motor and mental performance a few months after birth.

– Inevitably, the child dies after a few years.

3. Sickle-cell disease ‫.خاليا الدم الهاللية‬

– It is caused by the substitution of a single amino acid in

hemoglobin.

– When oxygen levels in

the blood of an affected

individual are low,

sickle-cell hemoglobin

crystallizes into long

rods.

– This deforms red blood

cells into a sickle shape.

– Doctors can use regular

blood transfusions to

prevent brain damage

and new drugs to

prevent or treat other

problems.



• The two alleles are codominant as both normal and abnormal

hemoglobins are synthesized.

• Normally it is relatively unlikely that two carriers of the same rare

harmful allele will meet and mate.



• However, consanguineous mating ‫ ,زواج األقارب‬those between

close relatives, increase the risk.



– These individuals who share a recent common ancestor are more

likely to carry the same recessive alleles.





• Most societies and cultures have laws or taboos forbidding

marriages between close relatives.

B- Dominantly inherited disorders ‫الصفات المرضية السائدة‬

• Although most harmful alleles are recessive, many human disorders

are due to dominant alleles.



1. Achondroplasia, a form of dwarfism ‫ ,القزمية‬has an incidence of one

case in 10,000 people.

– Heterozygous individuals have the dwarf phenotype.

– Those who are not achodroplastic dwarfs are homozygous recessive for this

trait.

• Lethal dominant alleles are much less common than lethal recessives

because if a lethal dominant kills an offspring before it can mature and

reproduce, the allele will not be passed on to future generations.



2. Huntington’s disease: a degenerative ‫ ضُمور‬disease of the nervous system.

The dominant lethal allele has no obvious phenotypic effect until an

individuals is about 35 to 45 years old.

– The deterioration of the nervous system is irreversible and inevitably

fatal ‫.مُميت‬

• Recently, molecular geneticists have used pedigree analysis ‫تحليل السجل العائلى‬

of affected families to track down ‫ لنزع‬the Huntington’s allele to a locus

near the tip of chromosomes 4.

Many other disorders have a multifactorial ‫ متعدد العوامل‬basis.





– These have a genetic component plus a significant environmental

influence.

– Multifactorial disorders include heart disease, diabetes, cancer,

alcoholism, and certain mental illnesses, such a schizophrenia and

manic-depressive disorder.

– The genetic component is typically polygenic ‫.متعدد الجينات‬



• At present, little is understood about the genetic contribution to most

multifactorial diseases

THE CHROMOSOMAL BASIS

OF INHERITANCE



Section B: Sex Chromosomes









1. The chromosomal basis of sex varies with the organism

2. Sex-linked genes have unique patterns of inheritance

1. The chromosomal basis of sex varies with the organism



• In human and other mammals, there are

two varieties of sex chromosomes, X & Y.

– An individual who inherits two X

chromosomes usually develops as a female.

– An individual who inherits an X and a Y

chromosome usually develops as a male.



• This X-Y system of mammals is not the

only chromosomal mechanism of

determining sex.

• Other options include the X-0 (in locust)

system, the Z-W system (in birds), and the

haplo-diploid system (in bees).



• In Human, the SRY gene (Sex-determining

Region of the Y chromosome) modifies

embryonic gonads into testes.

• Females lack the SRY gene, thus, the

embryonic gonads develop into ovaries.

• In the X-Y system, Y and X chromosomes behave as

homologous chromosomes during meiosis.

– In reality, they are only partially homologous and rarely

undergo crossing over





• In both testes (XY) and ovaries (XX), the two sex

chromosomes segregate during meiosis and each

gamete receives one.

– Each egg receives an X chromosome.

– Half the sperm receive an X chromosome and half receive a Y

chromosome.





• Because of this, each conception has about a fifty-fifty

chance of producing a particular sex.

2. Sex-linked genes have unique patterns of inheritance



• The sex chromosomes, especially the

X chromosome, have genes for many

characters unrelated to sex.

• These sex-linked genes ‫جينات مرتبطة بالجنس‬

follow the same pattern of inheritance

as the white-eye locus in Drosophila.

• If a sex-linked trait is due to a recessive

allele, a female have this phenotype

only if homozygous.

– Heterozygous females will be carriers.

• Because males have only one X chromosome

(hemizygous), any male receiving the recessive allele

from his mother will express the trait.



• Therefore, males are far more likely to inherit sex-

linked recessive disorders ‫ مرض‬than are females.





‫الصفات المرتبطة بالجنس تورث لألبناء الذكور من األم‬

‫ الحامل لهذا النوع‬X ‫فقط ألنهم يرثون منها الكروموسوم‬

‫ ال يحمل شىء‬Y ‫من الـﭼـينات، حيث إن‬

Sex-linked disorders ‫األمراض المرتبطة بالجنس‬ in human.

1. Duchenne muscular dystrophy: ‫وهن العضالت‬

affects one in 3,500 males born in the United States.

– Affected individuals rarely live past their early 20s.

– This disorder is due to the absence of an X-linked gene for a key

muscle protein, called dystrophin.

– The disease is characterized by a weakening ‫ ضعف‬of the muscles and

loss of coordination ‫.فـقـد التوازن‬

ْ

2. Hemophilia: ‫ النزيف الدموى‬is a sex-linked recessive trait defined by

the absence of one or more clotting factors ‫.عوامل تجلط‬

– These proteins normally slow and then stop bleeding.

– Individuals with hemophilia have prolonged bleeding ‫نزيف مستمر‬

because a firm clot ‫ تجلط‬forms slowly.

– Individuals can be treated with intravenous injections of the missing

protein.

– This gene is transmitted to offspring via the mothers.

– Thus, Sons borne from hemophilic woman should be exempted ‫يستثنى‬ ُ

from circumcision ‫.الختان‬

3. Color blindness: ‫ عمى األلوان‬is a

disorder inherited as a recessive sex-

linked character and affect both males

and females.

– A color blind female (XaXa) may be born to

a color blind father (XaY) and a carrier

mother (XAXa)





• Although female mammals ‫ الثدييات‬inherit

two X chromosomes, only one X chromosome is active.

• Therefore, males and females have the same effective dose (one

copy ) of genes on the X chromosome.

– During female development, one X chromosome per cell condenses into

a compact object, a Barr body ‫( جسم بار‬in somatic cells).

– This inactivates most of its genes.

• The condensed Barr body chromosome is reactivated in ovarian

cells that produce ova.

Chromosomal aberration ‫.الشذوذ الكروموسومى‬

• It is common ‫ شائع‬in meiosis and includes:

a) Chromosomal deletions/translocations ‫نقص أو فقد جزء‬

 Homologous chromatids may break ‫ تـَنكسر‬and rejoin ‫و تلتحم مرة أخرى‬

at incorrect places, thus, one chromatid will loose more genes

than it receives.

b) Chromosomal duplications ‫( تضاعُف‬Polyploidy ‫.)تعدد الكروموسومات‬

 result from nondisjunction ‫عدم اإلنفصال الكامل للكروموسومات أثناء اإلنقسام الميوزى‬

during gamete production in one parent.



• A diploid embryo that is homozygous for a large deletion

or male with a large deletion to its single X chromosome

is usually missing ‫ يفتقد‬many essential genes and this

ُِ

leads to a lethal ‫ مميت‬outcome.

– Duplications and translocations ‫ تغيير أماكن األجزاء المقطوعة‬are very harmful.



• Translocation or inversion can alter phenotype because

a gene’s expression is influenced by its location.

• Several serious human disorders are due to these

alterations ‫ تغييرات‬of chromosome number and structure.



• Although the frequency ‫ َيحدث مرارا‬of aneuploid zygotes

ُ

‫ الالقحة الـمتعددة الكروموسومات‬may be quite high in humans, most of

these alterations result in abortion ‫ إجهاض‬long time before

birth ‫.قبل الوالدة‬

– These developmental problems results from an imbalance

‫ عدم توازن‬among gene products.





• Certain aneuploid conditions decrease the imbalance

effect, leading to survival to birth ‫.المولود‬

– But these individuals have a set of symptoms ‫أعراض‬

َُ

(syndromes) characteristic ‫ مميـِزة‬of the type of aneuploidy as

following:-

A)- Aneuploidy (Chromosomal duplication) ‫,التعدد الكروموسومى غير التام‬





1- Down syndrome [Polyploidy (2n + 1), trisomy in autosomes]:

Is due to three copies of chromosome 21 (Trisomies ‫.)مجموعات كروموسومية ثالثية‬

Although chromosome 21 is the smallest human chromosome, it

severely alters ‫ يُغير‬an individual’s phenotype in specific ways.

• Most cases of Down syndrome result from nondisjunction

‫ عدم اإلنفصال الكامل للكروموسومات أثناء اإلنقسام الميوزى‬during gamete production in

one parent.

• The frequency ‫ تِكرار‬of Down syndrome correlates with the age of the

mother.

– This may be linked to some age-dependent abnormality in the spindle

checkpoint during meiosis I, leading to nondisjunction.





2- Klinefelter’s syndrome [Polyploidy (2n + 1), trisomy in sex chromosomes ],

(a)- An XXY male, occurs once in every 2000 live births.

• These individuals have male sex organs, but are sterile.

• There may be feminine characteristics ‫ ,له صفات أنثوية‬but their intelligence is

normal.

(b)- An XYY male, tend to somewhat taller than average.

(c)- A trisomy female (XXX), which occurs once in every 2000 live

births, produces healthy females.



3- Turner’s syndrome, a monosomy female (X0), which occurs

once in every 5000 births, produces phenotypic, but immature

females ‫.غير ناضجة جنسيا‬

B)- Chromosomal structure-alterations:

It can also cause human disorders.

• Deletions ‫ ,حزف‬even in a heterozygous state, cause severe physical

and mental problems.





1. Cri-du-chat ‫,عارض مواء القط‬

results from a specific deletion in chromosome 5.

– These individuals are mentally retarded, have a small head with

unusual facial features, and a cry like the mewing of a distressed cat.

– This syndrome is fatal in infancy ‫ الطفوية‬or early childhood.





2. Myelogenous, [leukemia (CML)].

Caused by chromosomal translocations since a fragment of

chromosome 22 switches places with a small fragment from the

tip of chromosome 9.

erozygous state, cause severe physical

and mental problems.





1. Cri-du-chat ‫,عارض مواء القط‬

results from a specific deletion in chromosome 5.

– These individuals are mentally retarded, have a small head with

unusual facial features, and a cry like the mewing of a distressed cat.

– This syndrome is fatal in infancy ‫ الطفوية‬or early childhood.





2. Myelogenous, [leukemia (CML)].

Caused by chromosomal translocations since a fragment of

chromosome 22 switches places with a small fragment from the

tip of chromosome 9.