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					                       Ch. 3
                   Molecules of Life
• Organic Compounds.
• Organic Molecules contain carbon & at least one hydrogen.
• Many organic compounds also contain O, N, S, P.
                       Carbon Is an Unique Element

                        Several factors make carbon essential to life:
CARBON                      The ease with which carbon atoms form bonds to
6p+ , 6e-                   other carbon atoms.
                            The strength of CC single bonds and the covalent
                            bonds carbon forms to other nonmetals, such as N,
            single          O, P, and S.
            covalent
            bond            Carbon can form 4 single covalent bonds.
                            These covalent bonds are very stable.

                  carbon
                  atom                                         Side chain




                                                          carbon backbone
                 Carbon Is a Unique Element

• Hydrocarbons
consist of hydrogen
atoms attached to a
carbon backbone.
 Ex. octane
Functional Groups



               • Organic compounds are
                      made up of a
                 carbon backbone with
                groups of atoms, called
                   functional groups,
                     attached to it.
Small Differences in Functional Groups Can Have
           a Large Effect On A Molecule!



   ESTROGEN                TESTOSTERONE
    How Do Cells Synthesize Organic Molecules?

• Small organic molecules (ex. Sugar) are used as subunits to
 synthesize longer molecules (ex. Starch).

• The small subunits are called monomers; long chains of monomers
 are called polymers.


• Subunits are joined together or split apart by two processes
 called condensation & hydration.
       How Do Cells Synthesize Organic Molecules?


Condensation
Two molecules combine.
Water molecule is formed.




Hydrolysis

A molecule splits into two
smaller ones.

Water molecule is used.
condensation & hydrolysis
       reactions
    The Organic Molecules

Four types:
 - Carbohydrates
 - Lipids
 - Proteins
 - Nucleotides
                     Carbohydrates

• Are “sugars”. Formula (CH2O)n .


•Contain an aldehyde or ketone group and one or more hydroxyl groups.


• Three types are: - Monosaccharide
                  - Oligosaccharide
                  - Polysaccharide
       Carbohydrates /       Monosaccharides
simplest sugars, monomers.
    • 6 carbon sugars
         - Glucose                          ALDEHYDE
                                             GROUP
         - Fructose                                                   KETONE
                                                                      GROUP
         - Galactose


    • 5 carbon sugars:
         - Ribose
         - Deoxyribose




                              Structure of glucose     Structure of fructose
       Carbohydrates /          Oligosaccharides
- short chain of covalentely bonded sugar monomers.
                      - Formed by condensation reaction.
         Disaccharides - consist of 2 sugars
                 ex. : - Sucrose
                       - Lactose
                       - Maltose




Formation
of a sucrose
molecule from         glucose                  fructose
two simple sugars
                                                     + H2O


                        SUCROSE (disaccharide)
            Carbohydrates /      Polysaccharides
 or complex carbohydrates are straight or branched chained sugar
 monomers.
    Common polysaccharides: - Starch - plants’ energy storage molecule
                            - Cellulose - plant cell wall
                            - Chitin - exoskeleton




Cellulose                                                          Starch chain
      Common Polysaccharide in Animals:
      GLYCOGEN: energy storage in animals




cellulose


amylose (a starch)




                                   glycogen
                                 Lipids
                             • Largely hydrocarbon
                           • Do not dissolve in water
                       • Dissolve in nonpolar substances




• Lipids with fatty acids
    - Glycerides
    - Phospholipids
    - Waxes

• Lipids with no fatty acids
    - Sterols
                              Fatty Acids

• Carbon backbone
• Carboxyl group (- COOH)
• Unsaturated
   – One or more double bonds in backbone
   – Liquid at room temp.
• Saturated
   – All single bonds in backbone
   – Solid at room temp.



                                            STEARIC   OLEIC   LINOLENIC
                                             ACID     ACID       ACID
                              Triglycerides
• Neutral fats                                GLYCEROL

   – Three fatty acids
     and a glycerol.
   – Formed by condensation
     reaction.
   – Body’s most abundant
     lipid.
   – Ex.
• Functions:
   – Energy reservoir
   – Insulation

                                                         TRIGLYCERIDE
                               THREE FATTY ACIDS              +
                                                             3H20
                            Examples of Waxes

• Long-chained fatty acids linked to alcohols or carbon
  rings


• Cover plant parts like leaves & fruits.
    – Help conserve water
    – Fend off parasites                                  Wax coating on fruits



• Animals, on feathers, skin, hair, etc.
    – Protect, repel water, lubricate




                                                          Honeycomb in a beehive
                              Phospholipids
• Glycerol backbone                             hydrophilic
                                                   head
• Two fatty acid tails (hydrophobic)             (orange)

• Phosphate-containing head
   (hydrophilic)
• Main materials of cell membranes
                                        hydrophobic
                                            tails




                                         One Kind Of
                                        PHOSPHOLIPID
                                Sterols
                                                       CHOLESTEROL


• Work as hormones & in cell membranes.
• EX. : Vitamin D, steroids, bile salts.


                                             sterol
                                           backbone




                                                      hydrophobic
                                                          tail
                                              •Ex. : collagen ,
                           Proteins                  keratin ,
                                                     albumin ,
•Are the most diverse biological molecules.          hemoglobin ,
•Functions:                                          antibody.
  -structural material
 -enzymes
 -storage
 -repair
 -anti-disease agents (antibodies)
 -hormones
•made of amino acids (a.a.)
   -20 different a.a.
   - polypeptides: chains of amino acids
                  Structure of Amino Acids
• Central carbon atom
• An amino group
• A carboxyl group                                                    carboxyl
                                            amino                     group
• A hydrogen atom                           group
• One or more atoms
  “R Group”                                                  R group

- What is in artificial sweetener
“aspartame”?




                                                    glutamine (glu)
   phenylalanine (phe)
                                    lysine (lys)
Proteins have four levels of structure

 1) primary - peptide bond
 2) secondary - hydrogen bonds
    - helix
    - pleated sheet

 3) tertiary - hydrogen & disulfide bonds
 4) quaternary - 2 or more polypeptide
   chains joined together
                     PROTEIN SYNTHESIS
Amino acids Join by peptide chains: amino group of one a.a. forms a
covalent bond with carboxyl group of another a.a.


                                                              •The order of
                                                               a.a. is one
                                                               way protein
                                                               structure
                                                               can differ.




                                                    newly
                                                    forming
                                                    polypeptide
                                                    chain
   Proteins have four levels of structure

• Hydrogen bonds
  – Helical coiling
  – Sheet-like pattern
                                         Secondary structure,
                                         such as this helix is
Proteins                                 maintained by
                                         hydrogen bonds.
have four
levels of
                                        Tertiary
structure:                              structure is
                                        illustrated by
1) primary                              folding of the
                                        helix, caused by
                                        disulfide bonds.
2) secondary
  - helix
  - pleated sheet
                    Primary structure
3) tertiary         is determined by
                    the sequence of
4) quaternary       amino acids
                    linked by peptide
                    bonds.




 Hemoglobin         Quaternary
                    structure is 2 or
 molecule with      more polypeptide
                    chains joined by
 4 heme groups.     hydrogen bonds &
                    covalent bonds.
                  Sickle-Cell Anemia

One amino acid change in
ß chain can have drastic   beta
                                       beta
effect on the hemoglobin   chain
                                       chain
molecule and finallly on
the shape of red blood
cells.


glutamate        valine




                            alpha      alpha
                            chain      chain
      How Can Protein Structure Change?
• denaturation
    - 3-D structure altered
    - due to change in pH or temp.

    - generally irreversible

    - ex. frying an egg



                          disulfide
                          bridges
                           Hair Cells Are Made of
                              Keratin Helices
                                              hair’s                    coiled keratin
                                              cuticle
                                                                        polypeptide
                                                                        chain


                                           keratin
dead, flattened cells      one hair cell   macrofibril
of a shaft of hair
                                                         microfibril (three polypeptide
                                                         chains coiled into one strand)



              Keratin molecules are held in their helical
              shapes by many hydrogen bonds.
                coiled keratin
                polypeptide
                                     Curliness of hair depends on number
                chain                     of disulfide bridges cross-linking
                                              various keratin molecules.




Straight hair    Curly hair     Permanent wave
                              growing out straight
                          Nucleotides
 •contain N base, 5C sugar, & a phosphate

1) adenosine phosphates
    •energy & signaling
    •e.g., ATP and cAMP

2) coenzymes
    •assist enzymes
    •carry H+ & or e-
       •e.g., NAD+, NADP+, FAD


3) nucleic acids
    •genetic info.
      •e.g., DNA & RNA
     The 4 Kinds of Nucleotide Bases Found in
                       DNA
            ADENINE                     THYMINE
            (N base)                    (N base)

phosphate
  group




              sugar



             GUANINE                    CYTOSINE
             (N base)                    (N base)
THE STRUCTURE OF DNA
The Structure Of DNA

				
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