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BASIC BIOCHEMISTRY
Biochemistry = the chemistry of life
Because carbon needs four electrons to fill its outer shell it can form
millions of different combinations with other atoms - ten times more than all
other atoms put together.
I. Organic molecules
A. Life as we know it is based on carbon
1. Carbon has four electrons in outer shell; bonds with up to four other
atoms (usually H, O, N, or another C)
2. Ability of carbon to bond to itself makes possible carbon chains and
rings which serve as the backbones of organic molecules
3. Organic molecules - contain carbon and hydrogen, most also
contain nitrogen, and oxygen
4. Functional groups - clusters of atoms with characteristic
structure and functions
B. Monomers and polymers
1. Most important biological compounds are polymers
a. Polymers - large compounds made of identical or nearly
identical repeating subunits
b. Monomers - the subunits of polymers
2. Making and breaking polymers
a. Condensation - making polymers by lining up monomers and
eliminating a water molecule, a hydroxyl (OH) group is removed from one
monomer and a hydrogen (H) is removed from the other
b. Hydrolysis - breaking polymers apart by introducing a water
molecule
PRINCIPLE ORGANIC POLYMERS
I. Carbohydrates - contain C, H and O in the proportion 1:2:1 (CH2O).
A. Most abundant organic compounds in nature
B. Serve both as structural compounds and as energy reserves to fuel life
processes
C. Carbohydrate monomers are called monosaccharides
1. Alpha glucose, a six carbon sugar (C6H12O6)
is the immediate energy source to cells
D. Carbohydrate polymers are called polysaccharides
1. Starch is straight chain of alpha glucose molecules with
few side branches, mostly from plant sources
2. Glycogen is highly branched polymer of alpha glucose with
many side branches; called "animal starch," it is storage
carbohydrate of animals
3. Cellulose is a polymer of beta glucose molecules, it is
primary constituent of plant cell walls
E. Disaccharides - 2 monosaccharides linked together
1. Sucrose (table sugar ) - glucose and fructose linked together
2. Lactose (milk sugar) is glucose + galactose
F. Virtually all carbohydrates come from plants which use the sun's energy
to make alpha and beta glucose.
II. Lipids - fats, oils, fatlike substances, some vitamins and
steroids
A. Primarily energy sources and structural compounds
B. Two principle characteristics:
1. Hydrophobic - insoluble in water
2. Large number of carbons with bonded hydrogens - therefore release a
larger amount of energy than other organic compounds. Fats yield 9 cal/gm,
carbohydrates 4 cal/gm
C. Major lipids:
1. Triglycerides (fats and oils) - three fatty acids joined to a
glycerol molecule:
a. Fatty acid - long hydrocarbon chains with terminal carboxyl (COOH)
group
Saturated fatty acids have no double bonds between their
carbon atoms
Unsaturated fatty acids have double bonds in the carbon chain
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% saturated/unsaturated fat in
some common foods
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Unsaturated
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Saturated
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| safflower |
72 |
beef |
48 |
| soybean |
59 |
butter |
55 |
| corn |
53 |
fish |
15 |
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coconut oil |
86 |
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chocolate |
56 |
b. Glycerol - three carbon molecule
1) Fats - triglycerides containing saturated fatty acids (e.g. butter
is solid at room temperature)
2). Oils - triglycerides with unsaturated fatty acids (e.g. corn oil
is liquid at room temperature)
c. Triglycerides are synthesized via condensation
2. Phospholipids - two fatty acids attached to phosphate group
a. phosphate heads are hydrophilic (water soluble) but tails are
hydrophobic (water insoluble) therefore they spontaneously line up to form
a lipid bilayer
b. very important because they form biological membranes
III. Polypeptides - polymers of nitrogen containing molecules called amino
acids, joined together by peptide bonds
A. Amino acids consist of:
1. Amino group - NH2 (positive charge)
2. Carboxyl group - COOH (negative charge)
3. Central carbon atom
4. R group - different substitution to the molecule, determines nature
of the amino acid
B. About 50,00 different proteins in humans, serve a variety of functions:
1. Structural - e.g. muscles, hair, fingernails, collagen
2. Enzymes - biological catalysts which regulate biochemical reactions
C. Proteins - large polypeptides with molecular weights from 10,000
- 1,000,000
D. Enzymes - large globular proteins from 12,000 to 1 million
molecular weights that act as catalysts
1. Catalysts - substances that accelerate chemical reactions but which
remain unchanged or unused in the process
2. Enzymes generally named by adding -ase to root name of substrate they
react upon, e.g. amylase breaks down amylose (starch)
E. Polypeptide structure - due to interactions between adjacent hydrogen
bonds and R groups proteins form complex three dimensional structures
C. Polypeptides can be denatured
1. Both temperature and pH can change polypeptide shape
a. Examples: heating egg white causes albumin to congeal; adding acid
to milk causes curdling. When such proteins lose their normal
configuration, the protein is denatured
b. Once a protein loses its normal shape, it cannot perform its usual
function
IV. Nucleic Acids - polymers of nucleotides
A. Nucleotides made up of:
1. Phosphate group - PO4
2. Five carbon sugar called ribose (or deoxyribose)
3. Nitrogenous base - ring structure containing C & N
B. Nucleotides have metabolic functions in cells:
1. Coenzymes are molecules which facilitate enzymatic reactions
2. ATP (adenosine triphosphate) - universal energy carrying
molecule
3. Nucleotides also serve as nucleic acid monomers
C. Nucleic Acids:
1. DNA (deoxyribonucleic acid) - the molecule which stores
the genetic information passed on from parent to offspring
2. RNA (ribonucleic acid) - serves as the translator of the
genetic information contained in DNA
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