BIO Lecture 6: Intro to Metabolism and Redox

First off, those of you that have taken biochemistry or have studied cellular respiration extensively can breathe easy--relative to its true complexity, MCAT metabolism is a joke. Forget the seemingly endless array of names in each pathway and throw away all of your flash cards, it's just the bare bones here. Let us begin.

Metabolism is the essentially the set of chemical reactions that occur in a cell to maintain life. Metabolism is generally divided into 2 categories, catabolism and anabolism.

Definitions you should know:
Catabolism: the process of breaking down molecules; includes breaking down and oxidizing food molecules (as we oxidize food, we release the stored energy that plants got from the sun). The purpose of catabolic reactions is to provide the energy and components necessary for anabolic reactions. Example: we extract glucose through oxidative catabolism (more on glycolysis later)
Anabolism: is "building-up" and the opposite of catabolism; think of this as constructive
Photosynthesis: the process by which plants store energy from the sun
Photoautotrophs: organisms (plants) that use energy from light (photo) to make their own (auto) food
Chemoheterotrophs: use the energy of chemicals (chemo) produced by other (hetero) living things; this is what humans are

The production and utilization of energy boil down to a series of oxidation/reduction reactions. Let's define what this means.

The three Meanings of Oxidize:
1. Attach oxygen or increase number of bonds to oxygen
2. Remove hydrogen
3. Remove electrons

The three Meanings of Reduce:
1. remove oxygen or decrease number of bonds to oxygen
2. add hydrogen
3. add electrons

When you reduce something, it's like compressing a spring--you store potential energy. The reduced substance wants to be oxidized back to where it started. NOTE: When one atom gets reduced, another must be oxidized. This is what is meant by the term redox pair.