Orientation to the Human Body

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Orientation to the Human Body Powered By Docstoc
					Anatomy & Physiology I
Chapter 3
All organisms composed of cells and cell products.
The cell is the smallest structural and functional
unit of life.
An organism’s structure and functions are due to
the activities of its cells.
Cells come only from preexisting cells, not from
nonliving matter.
Cells of all species have many fundamental
similarities in their chemical composition and
metabolic mechanisms.
Over 200 different types of human cells
Types differ in size, shape, subcellular
components, and functions
Squamous - thin and flat with nucleus creating bulge
Polygonal - irregularly angular shapes with 4 or more
sides
Stellate – starlike shape
Cuboidal – squarish and about as tall as they are wide
Columnar - taller than wide
Spheroid to Ovoid – round to oval
Discoid - disc-shaped
Fusiform - thick in middle, tapered toward the ends
Fibrous – threadlike shape
Squamous           Cuboidal             Columnar




Polygonal          Stellate             Spheroid




 Discoid    Fusiform (spindle-shaped)   Fibrous
                                           Erythrocytes
                      Fibroblasts




 Epithelial cells
 (a) Cells that connect body parts,
                                                                         Nerve cell
     form linings, or transport gases

Skeletal
                                    Smooth                (e) Cell that gathers information
Muscle
                                    muscle cells              and control body functions
cell


 (b) Cells that move organs and
                                                                                      Sperm
     body parts
                       Macrophage                         (f) Cell of reproduction

           Fat cell


(c) Cell that stores            (d) Cell that
nutrients                           fights disease
All cells have some common structures
and functions
Human cells have three basic parts:
  Plasma membrane—flexible outer boundary
  Cytoplasm—intracellular fluid containing
  organelles
  Nucleus—control center
ZOOMING IN
• What is attached to
the ER to make it look
rough?
• What is the liquid
part of the cytoplasm
called?
Regulates the movement of substance into and
out of the cell
Encloses cell contents
Separates intracellular fluid (ICF) from
extracellular fluid (ECF)
   Interstitial fluid (IF) = ECF that surrounds cells
Participates in cellular activities
Bilayer structure
   Phospholipids
   Cholesterol
   Proteins
75% phospholipids (lipid bilayer)
   Phosphate heads: polar and hydrophilic
   Fatty acid tails: nonpolar and hydrophobic
5% glycolipids
   contributes to glycocalyx – carbohydrate coating on
   the
   cells surface
20% cholesterol
   Increases membrane stability and fluidity
ZOOMING IN
• How many
layers make up
the main
substance of the
plasma
membrane?
             Chemical              Breakdown
             messenger             products
                                                                   Ions                                                CAM of
                                                                                                                       another cell




(a) Receptor             (b) Enzyme            (c) Ion Channel            (d) Gated ion channel   (e) Cell-identity marker   (f) Cell-adhesion
   A receptor that           An enzyme that        A channel protein          A gated channel         A glycoprotein             molecule (CAM)
   binds to chemical         breaks down           that is constantly         that opens and          acting as a cell-          A cell-adhesion
   messengers such           a chemical            open and allows            closes to allow         identity marker            molecule (CAM)
   as hormones sent          messenger and         ions to pass               ions through            distinguishing the         that binds one
   by other cells            terminates its        into and out of            only at certain         body’s own cells           cell to another
                             effect                the cell                   times                   from foreign cells
Unique fuzzy coat external to the plasma
membrane
   carbohydrate moieties of membrane glycoproteins
   and glycolipids
   unique in everyone, but identical twins
Functions
   protection               - cell adhesion
   immunity to infection    - fertilization
   defense against cancer - embryonic development
   transplant compatibility
Structures projecting from the cell surface used
   for motion
   Cilia
   Flagellum
Cilia




        10 m
     Motile cilia – respiratory tract, uterine tubes, ventricles
     of the brain, efferent ductules of testes
         beat in waves
         sweep substances across surface in same direction
         power strokes followed by recovery strokes


      Mucus
 Saline layer

Epithelial cells




                                     1 2 3 4       5    6           7
                                    Power stroke       Recovery stroke
Saline layer at cell surface due to chloride pumps move
Cl- out of cell. Na+ ions and H2O follow
Cystic fibrosis – hereditary disease in which cells make
chloride pumps, but fail to install them in the plasma
membrane
   chloride pumps fail to create adequate saline layer on cell
   surface
thick mucus plugs pancreatic ducts and respiratory tract
   inadequate digestion of nutrients and absorption of oxygen
   chronic respiratory infections
   life expectancy of 30          Mucus
                                Saline layer

                              Epithelial cells
tail of the sperm - only functional flagellum
whiplike structure
   much longer than cilium

movement is more snakelike
   no power stroke or recovery stroke as in cilia
Located between plasma membrane and
nucleus
Cytosol
   Water with solutes (protein, salts, sugars, etc.)
Cytoplasmic organelles
   Metabolic machinery of cell
Inclusions
   Granules of glycogen or pigments, lipid droplets,
   vacuoles, and crystals
Nucleus - Contains chromosomes (DNA) and nucleolus
Rough ER - Manufactures all secreted proteins
Smooth ER – Synthesize steroids and other lipids;
manufactures all membranes of the cell
Ribosomes - Site of protein synthesis
Mitochondria – cellular respiration (ATP production)
Golgi apparatus – Storage warehouses of the cell;
carbohydrate synthesis
Lysosomes - contain digestive enzymes; Digest ingested
bacteria, viruses, and toxins
Peroxisomes - Detoxify harmful or toxic substances;
Neutralize dangerous free radicals
Centrioles - play role in cell division
Largest organelle in a cell
  Genetic library with blueprints for nearly all
  cellular proteins
  Responds to signals and dictates kinds and
  amounts of proteins to be synthesized
  Most cells are uninucleate
  Red blood cells are anucleate
  Skeletal muscle cells, bone destruction cells, and
  some liver cells are multinucleate
                        Nuclear pores
Nuclear envelope        Nucleus
Chromatin (condensed)
Nucleolus




Cisternae of rough ER
DNA and RNA have similar structures
  Four nucleotides
     Adenine (A)
     Guanine (G)
     Cytosine (C)
     Thymine (T) or uracil (U)
  Sugar
     Ribose or deoxyribose
  Phosphate
  Nitrogen base
                       a long
DNA – deoxyribonucleic acid -
                                                                                  Adenine
threadlike molecule with                                                               NH2


uniform diameter, but varied                                                  N
                                                                                   C
                                                                                        C
                                                                                             N
                                                                         HC
length                                                                        N
                                                                                   C
                                                                                        N
                                                                                             CH
                                                                              H
    46 DNA molecules in the nucleus of most human        O
    cells
                                                    HO   P    O   CH2         O
DNA and other nucleic acids                              OH
                                                                  H H               H H
are polymers of nucleotides
                                                                    OH              H

Each nucleotide consists of                         Phosphate           Deoxyribose

    one sugar - deoxyribose
    one phosphate group
    one nitrogenous base
       A, T, G or C
                                                            Molecular shape is a double helix
                                                            (resembles a spiral staircase)
                  G
                  T
                          A           T
                                      C
                                          A
                                                                each sidepiece is a backbone
                  A               T
                                                                composed of phosphate groups
                                                                alternating with the sugar
                      G           C

             T                            A


             G                        C

                 A            T
                                                                deoxyribose.
                      C               G




                                          T
                                                               steplike connections between
                 G
                                          C                    the backbones are pairs of
             T
                                  A
                                                               nitrogen bases
                                          C
                  G




Sugar–phosphate                           Sugar–phosphate
backbone                                  backbone
Nitrogenous bases united by
hydrogen bonds                                             C       G



   a purine on one backbone with a                                 T
   pyrimidine on the other
   A – T two hydrogen bonds
                                                                   C
   C – G three hydrogen bonds                              G




DNA base pairing                                       T
                                                               A

     A–T
     C–G                                                           C
                                                           G


Law of Complementary Base
Pairing                              Sugar–phosphate                   Sugar–phosphate
                                     backbone                          backbone
   one strand determines base
   sequence of other
Genes – genetic instructions for synthesis of
proteins
Gene – segment of DNA that codes for a specific
protein
Genome - all the genes of one person
   humans have estimated 25,000 to 35,000 genes
     2% of total DNA
     other 98% is noncoding DNA
        plays role in chromosome structure
        regulation of gene activity
        no function at all – “junk” DNA
chromatin – fine filamentous DNA
material complexed with proteins                                              2 nm   1   DNA double
                                                                                         helix


   occurs as 46 long filaments called                       Core particle
   chromosomes                                        Linker DN
                                                              A               11 nm 2    DNA winds
                                                                                         around core
   in nondividing cells, chromatin is so                   Nucleosome
                                                                                         particles to form
                                                                                         nucleosomes
   slender it cannot be seen with light                                                  11 nm in
                                                                                         diameter
   microscope                                                                         Nucleosomes
                                                                              30 nm 3
                                                                                      fold accordion-
   histones – disc-shaped cluster of eight                                            like into zigzag
                                                                                      fiber 30 nm in
   proteins                                                                           diameter
                                                                            300 nm 4 30 nm fiber is
                                                                                      thrown into
   DNA molecule winds around the cluster                                              irregular loops
                                                                                      to form a fiber
   appears to be divided into segments -     In dividing cells only                   300 nm thick
                                                                                     In dividing
   nucleosomes                                                              700 nm 5 cells, looped
                                                                                     chromatin coils
                                                                                     further into a
   nucleosome consists of :                                Chromatids Centromere
                                                                                     700 nm fiber to
                                                                                     form each
                                                                                     chromatid
      core particle – histones with DNA                                       700 nm 6 Chromosome

      around them                                                                      at the midpoint
                                                                                       (metaphase) of
                                                                                       cell division
      linker DNA – short segment of DNA
      connecting core particles
RNA much smaller cousin of DNA (fewer bases)
    messenger RNA (mRNA) over 10,000 bases
    ribosomal RNA (rRNA)
    transfer RNA (tRNA) 70 - 90 bases
    DNA averages 100 million base pairs

one nucleotide chain (not a double helix as DNA)
ribose replaces deoxyribose as the sugar

uracil replaces thymine as a nitrogenous base

Essential function
    interprets code in DNA
    uses those instructions for protein synthesis
    leaves nucleus and functions in cytoplasm
A segment of DNA that carries the code for a particular
protein
    The segment of DNA first codes for the production of a
    molecule of RNA
    The molecule of RNA then plays a role in synthesizing
    one or more proteins (protein synthesis)

The amino acid sequence of a protein is determined by
the nucleotide sequence in the DNA
Genome – all the DNA in one 23-chromosome set
   3.1 billion nucleotide pairs in human genome

46 human chromosomes comes in two sets of 23
chromosomes
   one set of 23 chromosomes came form each parent
   each pair of chromosomes has same genes but different
   versions (alleles) exist
body can make millions of different proteins, all from the same 20
amino acids, and encoded by genes made of just 4 nucleotides
(A,T,C,G)
Genetic code – a system that enables these 4 nucleotides to code
for the amino acid sequence of all proteins
minimum code to symbolize 20 amino acids is 3 nucleotides per
amino acid
Base triplet – a sequence of 3 DNA nucleotides that stands for one
amino acid
    codon - the 3 base sequence in mRNA
    64 possible codons available to represent the 20 amino acids
       61 code for amino acids
       Stop Codons – UAG, UGA, and UAA – signal the ‘end of the message’, like a
       period at the end of a sentence
       Start Codon – AUG codes for methionine , and begins the amino acid sequence
       of the protein
process of protein synthesis
   DNA         mRNA           protein
transcription – step from DNA to mRNA
   occurs in the nucleus where DNA is located
translation – step from mRNA to protein
   most occurs in cytoplasm
   15-20% of proteins are synthesized in the nucleus
DNA too large to leave nucleus and participate directly in
cytoplasmic protein synthesis
    necessary to make a small mRNA copy that can migrate through a nuclear
    pore into the cytoplasm

Transcription – copying genetic instructions from DNA to RNA
translation – the process that converts the
language of nucleotides into the language of
amino acids
ribosomes - translate sequence of nucleotides
into the sequence of amino acids
   occur mainly in cytosol, on surface of rough ER, and
   nuclear envelope
                                  Nuclear
                                  envelope


                   DNA
   Transcription


  RNA Processing   Pre-mRNA


          mRNA
                               Nuclear
                               pores
                    Ribosome
Translation

   Polypeptide
1 DNA double helix




2 Seven base triplets on the
  template strand of DNA



3 The corresponding codons of
  mRNA transcribed from the
  DNA triplets

4 The anticodons of tRNA that
  bind to the mRNA codons



5 The amino acids carried by
  those six tRNA molecules

6 The amino acids linked into a
  peptide chain
                                         Gene (DNA)




   1 Transcription

                                         Pre-mRN A                 Intron   Exon

           A                 B       C                 D       E               F



   2 Splicing

               mRN A 1                    mRN A 2                   mRN A 3

       A            C            D   B        D            E   A      E            F



   3 Translation


                 Protein 1                 Protein 2               Protein 3




One gene can code for more than one protein
Defines changes from formation of the cell until
it reproduces
Includes:
   Interphase
   Cell division (mitotic phase)
Period from cell formation to cell division
Nuclear material called chromatin
Subphases:
   G1 (gap 1)—vigorous growth and metabolism
   S (synthetic)—DNA replication
   G2 (gap 2)—preparation for division
         S
         Growth and DNA
         synthesis      G2
                        Growth and final
G1                      preparations for
Growth                  division
                 M
Mitotic (M) phase of the cell cycle
Essential for body growth, tissue repair and
renewal
   Does not occur in most mature cells of nervous
   tissue, skeletal muscle, and cardiac muscle
Includes two distinct events:
  1. Mitosis—four stages of nuclear division:
        Prophase - Chromosomes become visible
        Metaphase - chromosomes are aligned at the equator
        Anaphase - Centromeres of chromosomes split
        simultaneously—each chromatid now becomes a
        chromosome
        Telophase - chromosomes uncoil to form chromatin
  2. Cytokinesis—division of cytoplasm by cleavage furrow
The stages of mitosis.
ZOOMING IN
• If the original cell shown
has 46 chromosomes, how
many chromosomes will
each new daughter cell
have?
plasma membrane – a barrier and a
gateway between the cytoplasm and ECF
  selectively permeable – allows some things through, and prevents other
  things from entering and leaving the cell

Some molecules easily pass through the
membrane; others do not
Travel across the membrane is based on
several factors:
  Molecular size
  Solubility
  Electrical charge
Diffusion through lipid bilayer
   Nonpolar, hydrophobic, lipid-soluble substances
   diffuse through lipid layer

Diffusion through channel proteins
   water and charged, hydrophilic solutes diffuse
   through channel proteins in membrane

Cells control permeability by regulating
number of channel proteins or by opening and
closing gates
Passive transport mechanisms
  Simple Diffusion
  Facilitated Diffusion
      Carrier-mediated facilitated diffusion
      Channel-mediated facilitated diffusion
  Osmosis
  Filtration
Passive transport mechanisms require no ATP.
  Random molecular motion of particles provides
  the necessary energy.
Active transport
  Carrier-mediated Active Transport
  Vesicular (Bulk) Transport
      Endocytosis
        Phagocytosis
        Pinocytosis
      Exocytosis
Active transport mechanisms consume ATP.
Simple Diffusion – the net
movement of particles from
area of high concentration to
area of low concentration             Down
                                      gradient
     due to their constant,
    spontaneous motion                Up
                                      gradient


Also known as movement
down the concentration
gradient – concentration of a
substance differs from one point to
another
                        Extracellular fluid

                                       Lipid-
                                       soluble
                                       solutes



Simple diffusion of
fat-soluble molecules
directly through the
phospholipid bilayer




                        Cytoplasm
facilitated diffusion - carrier-mediated transport
of solute through a membrane down its
concentration gradient
does not consume ATP
solute attaches to binding site on carrier, carrier
changes confirmation, then releases solute on
other side of membrane
               ECF




               ICF


                 1                               2                                    3
                     A solute particle enters        The solute binds to a receptor       The carrier releases the
                     the channel of a membrane       site on the carrier and the          solute on the other side of
                     protein (carrier).              carrier changes conformation.        the membrane.
              Lipid-insoluble
              solutes (such as                            Small lipid-
              sugars or amino                             insoluble
              acids)                                      solutes




                                 Channel-mediated facilitated
Carrier-mediated                 diffusion
facilitated diffusion            mostly ions selected on basis of size and
                                 charge
   Filtration - process in which particles are driven through a
   selectively permeable membrane by hydrostatic pressure (force
   exerted on a membrane by water)
   Examples
        filtration of nutrients through gaps in blood capillary walls into tissue
        fluids
        filtration of wastes from the blood in the kidneys while holding back blood
        cells and proteins
                                             Solute

                                             Water

Figure - Blood pressure in capillary        Capillary wall

forces water and small solutes such as
                                             Red blood
salts through narrow clefts between          cell

capillary cells.                                                            Clefts hold back
                                                                            larger particles
                                                                            such as red blood
                                                                            cells.
Osmosis - flow of water from one side of a
selectively permeable membrane to the other
  from side with higher water concentration to the side with lower water
  concentration

Water diffuses through plasma membranes:
  Through the lipid bilayer
  Through water channels called aquaporins (AQPs)
                    Water
                    molecules




                                    Lipid
                                    billayer




               Aquaporin
(d) Osmosis, diffusion of a solvent such as
   water through a specific channel protein
   (aquaporin) or through the lipid bilayer
Water concentration is determined by solute
concentration because solute particles displace
water molecules
Osmolarity: The measure of total concentration
of solute particles
When solutions of different osmolarity are
separated by a membrane, osmosis occurs until
equilibrium is reached
      (a)   Membrane permeable to both solutes and water
Solute and water molecules move down their concentration gradients
in opposite directions. Fluid volume remains the same in both compartments.

   Left                Right                  Both solutions have the
   compartment:        compartment:           same osmolarity: volume
   Solution with       Solution with          unchanged
   lower osmolarity    greater osmolarity



                 H2O

                Solute




                               Solute
                               molecules
   Membrane                    (sugar)
 (b)   Membrane permeable to water, impermeable to solutes
Solute molecules are prevented from moving but water moves by osmosis.
Volume increases in the compartment with the higher osmolarity.

                                          Both solutions have identical
                                          osmolarity, but volume of the
                                          solution on the right is greater
   Left             Right                 because only water is
   compartment      compartment           free to move




              H2O




                           Solute
                           molecules
 Membrane                  (sugar)



                                                                             Figure 3.8b
When osmosis occurs, water enters or leaves a
cell
Change in cell volume disrupts cell function
Tonicity - ability of a solution to affect fluid volume and pressure in
a cell; depends on concentration and permeability of solute
Hypotonic solution
    has a lower concentration of nonpermeating solutes than intracellular fluid
    (ICF)
       high water concentration
    cells absorb water, swell and may burst (lyse)

Hypertonic solution
    has a higher concentration of nonpermeating solutes
       low water concentration
    cells lose water + shrivel (crenate)

Isotonic solution
    concentrations in cell and ICF are the same
    cause no changes in cell volume or cell shape
     (a)   Isotonic solutions            (b)   Hypertonic solutions             (c)   Hypotonic solutions
Cells retain their normal size and     Cells lose water by osmosis and      Cells take on water by osmosis until
shape in isotonic solutions (same      shrink in a hypertonic solution      they become bloated and burst (lyse)
solute/water concentration as inside   (contains a higher concentration     in a hypotonic solution (contains a
cells; water moves in and out).        of solutes than are present inside   lower concentration of solutes than
                                       the cells).                          are present in cells).
active transport – carrier-mediated transport of solute
through a membrane up (against) its concentration
gradient
ATP energy consumed to change carrier
Examples of uses:
   sodium-potassium pump keeps K+ concentration higher inside
   the cell
each pump cycle consumes
one ATP and exchanges three
Na+ for two K+
                                               3 Na+ out


keeps the K+ concentration
higher and the Na+                                                    Extracellular
                                                                      fluid


concentration lower with in
the cell than in ECF
                                         ATP                         Intracellular fluid

necessary because Na+ and K+              ADP + P i
                                                           2 K+ in



constantly leak through membrane
   half of daily calories utilized for
   Na+ - K+ pump
Vesicular Transport – processes that move large particles, fluid
droplets, or numerous molecules at once through the membrane
in vesicles – bubblelike enclosures of membrane

Endocytosis –vesicular processes that bring material into the cell
    phagocytosis – “cell eating” - engulfing large particles
      macrophages

    pinocytosis – “cell drinking” taking in droplets of ECF
    containing molecules useful in the cell

Exocytosis – discharging material from the cell
                                                     Particle         1 A phagocytic cell encounters a
                                                                        particle of foreign matter.
               7 The indigestible
                 residue is voided by                                         Pseudopod
                 exocytosis.               Residue                                                   2 The cell surrounds
                                                                                                       the particle with its
                                                                Nucleus                                pseudopods.




                                                                           Phagosome
     6 The phagolysosome
       fuses with the                                                                                    3 The particle is phagocytized
                                                                            Lysosome                       and contained in a
       plasma membrane.
                                            Vesicle fusing                                                 phagosome.
                                            with membrane




                                                          Phagolysosome
                   5 Enzymes from the
                     lysosome digest the                                               4 The phagosome fuses
                     foreign matter.                                                     with a lysosome and
                                                                                         becomes a phagolysosome.




Keeps tissues free of debris and infectious microorganisms.
Taking in droplets of ECF
   occurs in all human cells

Membrane caves in, then
pinches off into the
cytoplasm as pinocytotic
vesicle
Certain mutations may cause changes in cells
  Uncontrolled reproduction of cells
  Cells spread (metastasize), producing cancer
  Cancer cells form tumors, crowding out normal
  cells
Certain forces increase the chances of developing cancer
  Heredity – individuals are more likely to develop certain
  types of cancers if they have a family history of cancer.
  Chemical carcinogens in cigarettes, foods, drugs, etc.
  Ionizing radiation from x-rays, UV rays and radioactive
  substances
  Continued physical irritation – increased cell division
  increases the chance of mutation
  Diets high in fats and low in fiber, fruits and vegetables
  make individuals more susceptible to digestive cancers
  Viruses trigger some cancers: cervical cancer,
  lymphomas, leukemias, liver cancer

				
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