Humber Admissions Practice Test

What does the Krebs cycle primarily generate?

1. Oxygen

2. ATP and carbon dioxide

3. Pyruvic acid

4. Lactate

The correct answer is: ATP and carbon dioxide

The Krebs cycle, also known as the citric acid cycle, plays a crucial role in cellular respiration, particularly in aerobic organisms. Its primary function is to generate energy through the oxidation of acetyl-CoA, which is derived from carbohydrates, fats, and proteins. During this cycle, one of the main outputs is ATP (adenosine triphosphate), the energy currency of the cell. Additionally, the cycle produces carbon dioxide as a byproduct, which is then exhaled by organisms. The production of ATP occurs through substrate-level phosphorylation, where a phosphate group is directly transferred to ADP (adenosine diphosphate) to form ATP. Furthermore, important electron carriers such as NADH and FADH2 are produced in this cycle, which are essential because they transport electrons to the electron transport chain, where a significant amount of ATP is generated through oxidative phosphorylation. In contrast, the other options do not accurately depict the primary outputs of the Krebs cycle. While pyruvic acid is a key intermediate in glycolysis leading up to the cycle, it is not generated by the Krebs cycle itself. Lactate is produced in anaerobic conditions, typically from pyruvate during fermentation, but this process is unrelated to the Krebs