The Krebs Cycle

by Nickolaos D. Skouras, PhD.

The Krebs cycle is also known as the TCA cycle or the Citric Acid cycle. It is used primarily for production of energy at the cellular level via production of ATP. These reactions occur in the mitochondria. The Krebs cycle can use fatty acids, proteins and glucose for energy production.

Coenzyme-A (CoA) is required to begin the cycle. Oxidized pyruvate combines with Coenzyme-A to yield Acetyl Coenzyme-A. One molecule of Acetyl-CoA produces 1 molecule of ATP (from GTP), 1 molecule of FADH2, and 3 molecules of NADH.

Next, Coenzyme-A delivers the acetyl group to oxaloacetate (OXA), a four carbon compound already present in the mitochondrion, with which the 2 carbon acetyl group combines to form citric acid. This step initiates the "first turn" of the Krebs cycle. At the end of the Krebs cycle, oxaloacetate has once again been formed. A second Acetyl-CoA combines with it, initiating the second turn of the Krebs cycle.

The Krebs cycle is diagrammed below.

The above information shows that for every 1 molecule of Acetyl-CoA that is created by Coenzyme-A, 3 molecules of NADH are produced. NADH is also known as "Coenzyme 1" and it is sold as a nutritional supplement called Enada. The above scientific and biological factual data indicates that "Coenzyme-A" supplementation is more essential than NADH (Enada) supplementation.