Mississippi MAAP Biology Practice Test

In the Kreb's Cycle, also known as the citric acid cycle or tricarboxylic acid cycle, the primary products include carbon dioxide, reduced coenzymes (NADH and FADH2), and a net gain of ATP. During each turn of the cycle, one ATP molecule is produced by substrate-level phosphorylation. Since the cycle runs twice for each glucose molecule that enters cellular respiration, it ultimately produces a total of 2 ATP molecules from one glucose.

The primary purpose of the Kreb's Cycle is to harvest high-energy electrons from acetyl-CoA, which enters the cycle after being derived from carbohydrates, fats, and proteins. These high-energy electrons are captured in the form of NADH and FADH2, which then carry the electrons to the electron transport chain, where they ultimately contribute to the production of a much larger amount of ATP.

In summary, while the Kreb's Cycle produces a small amount of ATP directly in the form of 2 ATP molecules, its most significant role is to generate reducing equivalents that power further ATP production during oxidative phosphorylation.