Question

Describe the structure and function of fatty acid molecules, including the difference between saturated and unsaturated fatty acids.

Answer 1

Fatty acids are fats that have acidic carboxyl groups on them. Something like
CH3-(CH2)n-COOH
Unsaturated fatty acids have double bonds between 1 or more of the carbons in the chain. They are unsaturated with hydrogen, but can be hydrogenated chemically.

Fatty acids have many roles, but a very common one is to form the lipids in membranes. In that case two fatty acids are usually joined to phosphate plus some other chemical groups.
For example, check out http://en.wikipedia.org/wiki/Phosphatidylcholine

Answer 2

When I said "fats" you should probably use the chemical name: alkanes.

Answer 3

T Elliott is quite right: "fat" or "lipid" is an ambiguous term. Or if it is not ambiguous to the chemists, who know exactly what the definition is, then it is used ambiguously by the biologists and biochemists.

A functional, biologist's definition would be: "A hydrocarbon containing molecule, where the bonds in the hydrocarbon chain are broken down to make energy or are used for structural purposes like maintaining cell membranes."

They use them for any type of hydrocarbon, which may or may not be correct. I'm no chemist. Alkanes are the single bond only (i.e., saturated) fats. Alkenes, alkynes, with one or more double and tripple bonds between the carbons respectively are unsaturated fats.

Answer 4

ὣς οἵ γ' ἀμφίεπον τάφον Ἕκτορος ἱπποδάμοιο