The Krebs Cycle

The Link Reaction

• The link reaction converts pyruvate to acetyl coenzyme A

1. Pyruvate is decarboxylated by the removal of one carbon as CO2 and forms acetate with the conversion of one NAD to NADH
2. It is then combined with coenzyme A to form acetyl coenzyme A
3. The acetyl coenzyme A is then transported to the next stage of respiration

The Krebs Cycle

• Forms NADH and CO2 from a series of oxidation-reduction reactions
• It takes place in the matrix of mitochondria

1. Acetyl coenzyme A combines with a 4-carbon molecule to form a 6-carbon molecule.
2. The 4-carbon molecule is converted to a 5-carbon molecule by releasing CO2 and forming one NADH from NAD.
3. The 5-carbon molecule is converted back into the original 4-carbon molecule, forming one CO2, two NADH from NAD, one ATP from ADP + Pi, and one FADH from FAD.
   1. FAD is a coenzyme like NAD but with a slightly different structure though it has a similar function
4. The ATP, NADH and FADH move on to the next stage of respiration while the 4-carbon molecule combines with another acetyl coenzyme A and carries out the cycle again.