The Krebs cycle (citric acid cycle) is a cyclical metabolic pathway that oxidizes acetyl-CoA to carbon dioxide and water, forming a molecule of adenosine triphosphate (ATP).
In addition to producing one ATP molecule, the series of redox reactions that form the Krebs cycle involve the transfer of electrons.
This electron transfer leads to the formation of three nicotinamide adenine dinucleotide (NADH) molecules and one flavin adenine dinucleotide (FADH2) molecule.
The Krebs cycle involves a total of nine reactions.
At the end of the cycle, the glucose molecule that entered glycolysis has been completely catabolized.
By the end of the Kreb’s cycle, energy contained in the original molecule of glucose has been used to form four ATP molecules and 12 electron carriers.