Citric Acid Cycle

The citric acid cycle, also known as the Krebs cycle or tricarboxylic acid (TCA) cycle, is a series of chemical reactions in the cell that breaks down food molecules into carbon dioxide, water, and energy. In plants and animals, these reactions take place in the mitochondria of the cell as part of cellular respiration. Many bacteria perform the citric acid cycle too, though they do not have mitochondria so the reactions take place in the cytoplasm of bacterial cells. Sir Hans Adolf Krebs, a British biochemist, is credited with discovering the cycle. Sir Krebs outlined the steps of the cycle in 1937.

The overall reaction for the citric acid cycle is:

Acetyl-CoA + 3 NAD⁺ + Q + GDP + P_i + 2 H₂O --> CoA-SH + 3 NADH + 3 H⁺ + QH₂ + GTP + 2 CO₂

where Q is ubiquinone and P_i is inorganic phosphate