Why Is the Krebs Cycle Called a Cycle?

Simple Explanation of Why the Krebs Cycle is Called a Cycle


The Krebs cycle, which is also known as the citric acid cycle or tricarboxylic acid cycle, is part of a series of chemical reactions that organisms use to break food down into a form of energy that cells can use. The cycle occurs in mitochondria of cells, using 2 molecules of pyruvic acid from glycolysis to produce the energy molecules. The Krebs cycle forms (per two molecules of pyruvic acid) 2 ATP molecules, 10 NADH molecules, and 2 FADH2 molecules.

NADH and the FADH2 produced by the cycle are used in the electron transport system.

The final product of the Krebs cycle is oxaloacetic acid. The reason the Krebs cycle is a cycle is because oxaloacetic acid (oxaloacetate) is the exact molecule needed to accept an acetyl-CoA molecule and start another turn of the cycle.

Which Pathway Produces the Most ATP?