EPOB 1210 Lecture 4 1996
Carbon and Molecular Diversity

Announcements:

EXAM 1 is Sept. 20, 1996

This has been the 1560th visit to this site since August 26, 1996.

Aside from water, most biologically important molecules are carbon-based (organic). The diversity of organic molecules results from the ability of C to form complex molecules by bonding to itself and elements such as H, O, N, S and P.

A. THE FOUNDATIONS OF ORGANIC CHEMISTRY

1. ORGANIC MOLECULE = Carbon Containing

2. VITALISM vs. MECHANISM

Vitalism = Belief in a life force outside of the laws of chemistry and physics. It was believed that only living organisms could synthesize organic molecules.

Mechanism = Belief that all natural phenomena are governed by physical and chemical laws.
Chemists finally synthesized organic molecules in the lab. Urea was synthesized in 1828.

B. CARBON IS VERY VERSATILE

1. ATOMIC No. = 6, therefore has 4 VALENCE e-
therefore forms 4 COVALENT BONDS
(See Fig. 4.2)

2. Allows COMPLEX/BRANCHING MOLECULES

3. COMPATIBILITY with many elements

e.g.
H (valence = 1)
O (val. = 2)
N (val. = 3)
can bond w/ all three

4. Determines 3-D shape ....... TETRAHEDRON

C. VARIATION IN CARBON SKELETONS
(See Fig. 4.4)

WAYS TO DRAW
E.G. BENZENE,
note that C always has 4 bonds

Some definitions:

1. HYDROCARBONS = CONTAIN ONLY C and H atoms.
Major components of fossil fuels
Components of molecules in living orgs.
e.g. fats

2. ISOMERS = Same molecular formula but different
structures.
(see Fig. 4.6)

3 types of isomers:

Structural Isomers = Variation in covalent arrangement

Geometric Isomers = Variation in arrangement around a double bond

Enantiomers = Mirror images

4 FUNCTIONAL GROUPS around one C

2 POSSIBLE arrangements around asymmetric C.

D. FUNCTIONAL GROUPS (see Table 4.1)

= CHEMICALLY REACTIVE GROUPS ATTACHED TO A MOLECULE

EXAMPLES:

1. HYDROXYL = -OH
POLAR (compare benzene and phenol)
makes molecule WATER SOLUBLE
ALCOHOLS have -OH groups

2. CARBONYL = =O
POLAR
makes molecule WATER SOLUBLE
SUGARS have =O groups
COMPARE KETONES AND ALDEHYDES

3. CARBOXYL = -COOH
POLAR
makes molecule WATER SOLUBLE and acidic
CARBOXYLIC ACIDS have -COOHs

4. AMINO group = -NH2
POLAR
makes molecule H2O SOLUBLE and basic
AMINES have amino groups

5. METHYL group = -CH3
NON-POLAR (remember methane CH4)
WATER INSOLUBLE (a Hydrophobic group)

6. PHOSPHATE group = H3PO4
POLAR
WATER SOLUBLE and ACIDIC
important in ENERGY METABOLISM and
MEMBRANE LIPIDS (more next week)
draw:

7. SULFHYDRYL group = -SH

EXAMPLE OF SEX HORMONES AND FUNCTIONAL GROUPS
(see FIG. 4.8)