Chapter 3:
THE CHEMISTRY OF ORGANIC MOLECULES
I. Living organization
A. Organic molecules: in living things, contain C bonded to H, and sometimes N, O, P
B. Inorganic molecules: found in nonliving matter
C. Carbon has 4 electrons in outer shell-can bond with 4 molecules
1. Usually bonds to hydrogen, oxygen, nitrogen. carbon
2. Ability to bond with itself results in long carbon chains >50
3. Carbon can also share two pairs of electron with another atom, giving a double
covalent bond
D. Functional Groups attached to carbon
1. Hydrophilic: polar molecule, + and -, attracted to H2O
2. Hydrophobic: nonpolar hydrocarbon, not attracted to H2O
3. Carboxyl: -COOH (acid)
4. Isomers: different arrangements of molecules with the same chemical formula
E. Building polymers
1. Monomer: a small organic molecule
2. Polymers: a large molecule made of monomers
a. polysaccharide monosaccharide
b. polypeptide amino acid
c. nucleic acid nucleotide
3. Synthesis by condensation (dehydration)-- a molecule of H2O is removed as 2
monomers join
a. hydroxyl group of one monmer and a hydrogen from the other.
b. usually requires enzyme
4. Breakdown by hydrolysis-- 2 molecules are broken apart by adding H2O,
releases energy
II. Carbohydrates--(CH2O), bear many hydroxyl groups, 4 cal/g
A. Function of carbohydrates
1. Sugars, starch, glycogen-energy storage
2. Cellulose-support
3. Membrane-bound carbohydrates--Self recognition
B. Sugars-Monosaccharides: simple sugars
1. 6 C sugars: glucose (C6H12O6), fructose, galactose
2. 5 C sugars: ribose (RNA), deoxyribose (DNA)
C. Disaccharides: 2 monosaccharides joined by condensation
1. Lactose: galactose + glucose
2. Maltose: glucose + glucose
3. Sucrose: glucose + fructose (table sugar)
D. Polysaccharides: many glucose molecules joined together
1. Starch: plant storage of glucose
a. few side branches
2. Glycogen: animal storage of glucose, liver
a. many side branches
b. branches allow breakdown at multiple sites.
c. bond orientation among glucose molecules allows formation
of compact spirals
3. Cellulose: used for plant structure, difficult to digest
a. forms straight fibers
b. unbranched polymers held together by hydrogen bond
c. cotton, lumber
d. not digestible
4. Chitin: glucose with an amino acid, in crab shells, fungi
a. linkage among glucose molecules like in cellulose
b. not digestible
III. Fatty Acids to Lipids: insoluble in water, 9 calories/g
A. Fats (solids) and Oils (liquids): energy storage
1. Glycerol: has 3 (hydroxyl) OH- groups attached, polar, mix with water
2. Fatty acids: long H-C chain with COOH attached:
3. Triglyceride: 3 fatty acids attached to a glycerol
4. Saturated fats: no C=C bonds (solid)
5. Unsaturated fats: has C=C bonds, better for us, (liquid)
6. Triglycerides containing fatty acids with unsaturated bonds melts at lower
temperature than those containing saturated fatty acids.
7. Fats-animal origin, Oils-plant originOils-plant origin
8. Animals use fat not glycogen for long-term energy storage.
B. Waxes: fatty acid added to an alcohol molecule
1. high melting temps, solid at normal temperatures
2. hydrophobic, waterproof
3. bees use wax to make comb within which they deposit honey which is
composed of sucrose breakdown products--glucose, fructose
C. Phospholipids
1. same as fats, except phosphate group in place of fatty acid
2. polar head, nonpolar tail=hydrocarbon tail
3. cell membranes-part phospholipid bilayer with polar end facing out
D. Steroids: backbone of 4 carbon rings
1. one of the most common steroids--cholesterol
2. precurosor of several other steroids
3. precursor to testosterone and estrogen-sex hormones
IV. Proteins: 4 calories/g, (amino) NH2 and (acid) COOH
A. Amino acids: (20) building blocks of proteins
1. three functional groups attached to carbon:
amino group, carboxyl group, and R- group
B. Peptide: 2 or more amino acids linked together
1. Peptide bond: covalent bond between 2 amino acids
2. Peptide bond is polar
3. Allows for hydrogen bonding between the -CO of one amino acid and the -NH
of another amino acid
D. Functional Roles of Proteins
1. Support: Keratin-makes up hair and nails
Collagen-support ligaments, tendons and skin
2. Enzymes: organic catalysts that speed up chemical reactions in cells without
being used up in the process
3. Transport-channel proteins in plasma membrane-enter, exit cell carrier proteins
in membrane transport within blood-hemoglobin
4. Defense-antibodies, proteins that combine with foreign substances.
5. Hormones: insulin controls glucose concentration growth hormone-height of
individual
6. Motion: actin and myosin-cause muscle cells to contract
E. Denatured: temperature and pH can disrupt the structure of a protein
1. Renaturation of protein and resumption of function proof that amino acid
sequence determined shape and function
F. Protein structure or shape
1. Primary structure: sequence of amino acids
2. Secondary structure:
a. 2 dimensional alpha helix or beta sheet
b. Discovered by Linus Pauling and Robert Corey in the late 1930s
c. Also includes -S-S- bonds between two cysteine amino acids
d. ex) hair, keratin where alpha helices bonded together by = disulfide
bonds.
3. Tertiary structure: 3D orientation (folding, twisting), globular
4. Quaternary structure: 4D orientation, more than 1 polypeptide, ex) hemoglobin
V. Nucleotides and Nucleic Acids
A. Nucleotides- composed of phosphate, 5 carbon sugar, and a nitrogen containing
base
B. Nucleic acids are polymers of nucleotides formed by condensation synthesis.
C. DNA (Deoxyribonucleic acid)
1. Four bases: (A) adenine, (T) thymine, (C) cytosine, (G) guanine
2. Double helix structure-two strands held together by H bonds
3. Sugar: deoxyribose (sides of ladder)
4. Contains genetic instructions
D. RNA (Ribonucleic acid)
1. Four bases: (A) adenine, (U) uracil, (C) cytosine, (G) guanine
2. Single strand
3. Sugar: ribose
4. Used to make proteins
E. Complimentary base pairing
1. Pyrimidines-thymine, cytosine and uracil-single ring
2. Purines-adenine, guanine-double ring
3. G-C and A-T always paired together
4. G-C bonds stronger than A-T bonds
C. ATP (Adenosine Triphosphate):
1. High energy molecule
2. Unstable phosphate bonds
3. ATP breakdown: ATP® ADP + P + energy
4. Energy released by ATP coupled to many energy requiring reactions-such
as those of macromolecules
5. Called the energy currency of cells