Acetyl coenzyme A

Acetyl coenzyme A (often abbreviated as Acetyl-CoA) is a crucial molecule in metabolism, used in many biochemical reactions. Its main function is to convey the carbon atoms within the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for energy production.

Structure

Acetyl-CoA is composed of an acetyl group attached to coenzyme A (CoA). CoA is a complex molecule that is made from pantothenic acid (vitamin B5) and adenosine triphosphate (ATP). The acetyl group (CH3CO) is linked to the sulfhydryl substituent of CoA through an ester bond.

Role in Metabolism

Acetyl-CoA plays a key role in the metabolism of carbohydrates, fats, and proteins. It is central to the balance between carbohydrate metabolism and fat metabolism. In carbohydrate metabolism, glucose is broken down by glycolysis to form pyruvate. Pyruvate is then oxidized to acetyl-CoA by the pyruvate dehydrogenase complex.

In fat metabolism, acetyl-CoA is the intermediate product in the breakdown of fats. Fatty acids are broken down in the mitochondria to form acetyl-CoA through a process called beta-oxidation.

In protein metabolism, acetyl-CoA is formed from the breakdown of certain amino acids.

Role in the Citric Acid Cycle

The primary role of acetyl-CoA in the body is to deliver the acetyl group to the citric acid cycle (Krebs cycle) for energy production. The acetyl group of acetyl-CoA enters the citric acid cycle and gets oxidized to CO2 while producing NADH and FADH2. These molecules then enter the electron transport chain, where they are used to produce ATP, the energy currency of the cell.

Role in Biosynthesis

Acetyl-CoA is also used in the biosynthesis of many important compounds and structures. For example, it is used in the synthesis of fatty acids and cholesterol. It is also used in the post-translational modification of proteins during protein synthesis.

See Also

• Metabolism
• Citric acid cycle
• Coenzyme A
• Glycolysis
• Beta-oxidation