In which type of organisms does the citric acid cycle occur?

The citric acid cycle, also known as the Krebs cycle or TCA cycle, is a crucial metabolic pathway that occurs in all aerobic organisms. This cycle plays a vital role in cellular respiration, where it helps convert carbohydrates, fats, and proteins into carbon dioxide, water, and energy stored in the form of ATP (adenosine triphosphate).

Aerobic organisms, which include animals, plants, and many fungi and bacteria, utilize oxygen for the oxidation of substrates in the citric acid cycle, leading to the production of energy. Since the cycle happens in the mitochondria of eukaryotic cells and the cytoplasm or cell membrane of prokaryotic organisms, it underscores its universal significance across diverse life forms that rely on aerobic metabolism.

The other mentioned options refer to more limited categories of organisms. While plants do indeed participate in the citric acid cycle, they are not the only type of organisms that do so. Animals also engage in this cycle for energy production. Anaerobic organisms, which do not require oxygen, primarily rely on fermentation processes and do not utilize the citric acid cycle or do so in a very modified manner, further emphasizing that the cycle's occurrence is fundamentally linked to aerobic processes.