Question

1. Would a saturated fatty acid hold more potential energy or less potential energy than an unsaturated fatty acid? Why? Be sure to frame your answer in terms of the redox state of the carbon atoms within each molecule.

2. Photosynthesis utilizes light energy in order to synthesize glucose molecules from carbon dioxide. Describe the process by which cells capitalize on the energy carried by photons to do work.

3. Some proteins have unstructured domains. This seems counterintuitive given the role of structure in defining function. How would you explain to someone new to biology that these unstructured regions are just an extension of the idea of structure defining function?

Answer 1

Answer 1: Fatty acids usually can differ in the number of carbon atoms or in length and also, by their degree. This differentiates between the types of fatty acids.

Saturated fatty acids are the ones that hold single bonds with their adjacent neighbors in the chain of hydrocarbon whereas, the unsaturated fatty acids possess the double bonds and have fewer hydrogens compared to saturated fatty acids. This unsaturated fatty acid can further be grouped into mono or poly depending on the bond. For example, if it has one bond, it is said to be monosaturated fatty acids whereas, for two bonds it is called poly saturated fatty acids.

It also gives two configurational stages like cis or trans. This depends on whether two hydrogens are attached on the same side (cis) otherwise (trans) opposite sides.

For saturated fatty acids, the oxidation is usually favored that requires the FAD+ that forms FADH2 (the expenditure of energy is equivalent to 1.5 ATP in this case).

[ ATP is the energy currency of cells which is generally stored and required by the body to favor energetically coupled reactions.]

Whereas, for unsaturated fatty acids, the beta-oxidation usually is an unfavorable process because of the presence of cis configuration that may occur in them. The possible enzyme is needed for the reaction which requires the NADPH this makes firstly, the bond shift from cis to trans face and then the oxidation is carried out. As we know that NADPH (the expenditure of energy here is equivalent to 2.5 ATP in this case).

So, due to the high expenditure of energy for making this double bond shift from cis to trans face ultimately produces less energy compared to the saturated fatty acids.

Example:

· Linoleic acid       (C18H32O2)

This has 18 carbons chain and two double bonds. This possesses a cis configuration. 18:2

· Steric acid (C17H35CO2H)

This also has 18 carbon atoms and no double bonds. 18:0