Tricarboxylic acid cycle (TCA)

Definition

The tricarboxylic acid cycle (TCA), also known as the Krebs cycle or citric acid cycle, is a series of enzymatic reactions in the mitochondrial matrix that oxidize acetyl-CoA to CO₂ and H₂O. It plays a crucial role in cellular respiration by generating high-energy electron carriers used in the electron transport chain.

5 Must Know Facts For Your Next Test

1. The TCA cycle begins with the condensation of acetyl-CoA and oxaloacetate to form citrate.
2. One turn of the TCA cycle produces three NADH molecules, one FADH₂ molecule, and one GTP/ATP.
3. The main function of the TCA cycle is to produce high-energy electron carriers (NADH and FADH₂) for ATP production via oxidative phosphorylation.
4. Key enzymes in the TCA cycle include citrate synthase, aconitase, isocitrate dehydrogenase, and α-ketoglutarate dehydrogenase.
5. The TCA cycle also provides intermediates for biosynthetic pathways, including amino acids and nucleotide synthesis.

Review Questions

• What are the main products generated by one turn of the TCA cycle?
• Which molecule combines with acetyl-CoA to initiate the TCA cycle?
• Why is the TCA cycle considered central to both catabolic and anabolic processes?

Related terms

Glycolysis:

A metabolic pathway that breaks down glucose into pyruvate, yielding ATP and NADH.

Oxidative Phosphorylation:

A process occurring in mitochondria that uses oxygen and high-energy electrons from NADH and FADH₂ to produce ATP.

Acetyl-CoA:

A molecule that conveys carbon atoms within cells for metabolism in both the TCA cycle and fatty acid synthesis.