Question

Respiratory pathway is believed to be a catabolic pathway. However, nature of the TCA cycle is amphibolic. Explain.

Answer 1

Amphibolic pathway:

Biochemical pathways in which both anabolism and catabolism occur is called an amphibolic pathway.

TCA cycle as an amphibolic pathway:

$\bullet$ In the TCA cycle, acetyl CoA produced from the pyruvic acid is metabolised (catabolic reaction) further to release $C{O}_2$ gas.

$\bullet$ During fatty acid formation (anabolism) acetyl CoA is withdrawn from the TCA cycle.

$\bullet$ Thus, in the TCA cycle both anabolism and catabolism occur. Therefore, it is an amphibolic pathway.