How Do Fatty Acids Enter the Citric Acid Cycle?

Fatty acids provide energy through the citric acid cycle.

Fatty acids, metabolized to the molecule acetyl-CoA, are the main input for the citric acid cycle that provides our bodies with cellular energy.

Ciitric Acid Cycle

The citric acid cycle, or Kreb's cycle, is a series of chemical reactions that produce raw materials and energy for cell survival. The starting point of the citric acid cycle is the molecule acetyl-Co-enzyme A, or acetyl-CoA.

Fatty Acids

Dietary fats (triacylglycerols) are three linked molecules of fatty acids. Fatty acids are broken down by a process called beta oxidation to the molecules fatty acyl-CoA and acetyl Co-A, the starting point of the citric acid cycle.

Fatty Acid Oxidation

In a series of four chemical reactions, beta oxidation of a fatty acid yields a fatty acyl-CoA that is two carbon atoms shorter than the original fatty acid, plus one molecule of acetyl-CoA. The series of reactions continues until the fatty acyl-CoA is completely cut up into acetyl-CoA.

Acetyl-CoA

Acetyl-CoA comes from the breakdown of fatty acids, carbohydrates and amino acids. In the first step of the citric acid cycle, acetyl-CoA is converted to citrate.

Fun Fact

Fats are better energy sources than sugar: the chemical break-down of fatty acids in the citric acid cycle yields six times more cellular energy than an equal weight of glycogen (the storage form of glucose).

References

• Biochemistry; Donald Voet and Judith G. Voet; 1990