CHAPTER 3 BIOCHEMISTRY
3-2 CARBON COMPOUNDS
3-2
A.
CARBON BONDING
- carbon readily forms four covalent bonds with other atoms; bonds with
other carbon atoms, creating huge and diverse variety of organic
compounds; carbon can form single, double or triple bonds; rings, chains
or branched chains
B.
FUNCTIONAL GROUPS
- clusters of atoms which influence the properties of the molecules they
are attached to
- an example = alcohol -OH (hydroxyl) group – this makes alcohol a polar
molecule; -COOH (carboxylic acid); -NH2 (amino group); CH3 (methyl
group
C.
LARGE CARBON MOLECULES
- monomers = small molecules that serve as building blocks
- monomers join together to form polymers (repeated linked units)
- units may be structurally identical or similar
- large polymers = macromolecules
- monomers form polymers through dehydration synthesis, in which a
water molecule is lost from the two molecules joined together
- when polymers are broken down into smaller molecules, hydrolysis, a
molecule of water is added to replace electrons lost by breaking of
bond between two molecules
D.
ENERGY CURRENCY
- biological processes need a constant supply of energy
- ATP = adenosine triphosphate
- terminal phosphate bond is an unstable, high energy bond
MOLECULES OF LIFE
A.
CARBOHYDRATES
- C, H, O in a 1:2:1 ratio
- energy storage, energy on the spot, structural integrity
1.
Monosaccharides
- simple sugars; most common: glucose, fructose, and galactose
- glucose = main energy source for cells
-
2.
fructose = fruit sugar
galactose = milk sugar
all three have same molecular formulae, but different structures,
hence, different chemical properties = these are isomers
Disaccharides + Polysaccharides
- disaccharide = double sugar
- examples: sucrose (table sugar), maltose (beer sugar), and lactose (milk
sugar)
- polysaccharides = three or more monosaccharides
- examples:
- glycogen – stored sugar in animals (found primarily in muscle and liver)
- starch – stored sugar in plants
- cellulose – responsible for plant rigidity and strength (major component
of cell walls)
- chitin – insect exoskeletons
B. LIPIDS
- large, nonpolar (hydrophobic, water hating) organic molecules that do not dissolve
in water
- C,H,O in no particular ratio
- energy storage, cell membrane structure, hormones, insulation, protection
1. Fatty Acids
- unbranched carbon chains that make up most lipids
- COOH group is the carboxyl group
- hydrophobic
- saturated vs unsaturated fatty acids
2. Complex Lipids
- triglycerides – 3 fatty acids joined to one glycerol molecule (alcohol)
- phospholipids – 2 fatty acids joined to a glycerol molecule and a
phosphate group – forms cell’s barrier
- wax – protection – waterproof
3. Steroids
- four fused carbon rings with other functional groups attached to them
- hormones; cholesterol (needed by nerve cells)
C. PROTEINS
- made of C,H,O,N and sometimes S
- animal skin and muscle is mostly protein and many biological catalysts in
plants and animals
1.
Amino Acids
- about 20 common – building blocks of protein (monomers)
- a central carbon bonded to a hydrogen, an amino group and a hydroxyl
group and something known as the “R” group
- difference between animo acids is found in the R group
- R groups determine final protein shape
2.
Dipeptides and Polypeptides
- when two amino acids join together in a condensation reaction
(dehydration synthesis), a special covalent bond is formed (peptide
bond)
- polypeptides are very long chains of amino acids – some proteins are
formed of more than one polypeptide chain
- these chains fold and bend because of hydrogen bonding and
hydrophobic and hydrophilic interactions of amino acid R groups
- Primary structure – chains of amino acids
- Secondary structure – hydrogen bonding between amino acids causes
coils to form (alpha helix)
- Tertiary structure – R group interactions
- Quaternary structure – two or more tertiary structures
Enzymes
- biological catalysts
- lock and key fit between an enzyme and its susbtrate
- this causes stress on the chemical bonds of the substrate; activation
energy is lowered
- the enzyme itself is unchanged; it can be used over and over
- change in pH or temperature can cause a change in the shape of the
enzyme -> reaction will not occur (CAN YOU SAY “HOMEOSTASIS”?)
- Activation energy = energy needed for a chemical reaction to occur
3.
D. NUCLEIC ACIDS
- very large and complex
- store hereditary information in cell
- DNA = deoxyribonucleic acid = stores information controlling cellular
activities; found in linear form (chromosomes) in nucleus of eukaryotic
cells and in circular chromosomes in prokaryotic cells
- RNA = ribonucleic acid = helps manufacture proteins using directions
from DNA
- building blocks are nucleotides = a 5 carbon sugar (deoxyribose or
ribose), a phosphate group and a nitrogenous base (adenine, guanine,
cytosine and thymine)
- In RNA, thymine is replaced with uracil