Question

Which among the following is NOT an amphibolic pathway?

• A. TCA cycle
• B. EMP pathway
• C. Calvin cycle
• D. Glycolysis

Answer 1

The correct option is C Calvin cycle

Amphibolic pathways are those biological pathways that involves both catabolic (break down) and anabolic (build up) pathways. Respiratory pathways like glycolysis (or EMP pathways) and TCA cycle (Krebs cycle) are amphibolic pathways.

In EMP pathway or glycolysis, glucose is broken down into pyruvate (catabolic pathway) but at the same time the substrates like pyruvate can also be used in the biosynthesis of glucose in gluconeogenesis (anabolic pathway). So, EMP pathway or glycolysis is an amphibolic pathway.

In TCA cycle, acetyl CoA enters the cycle and releases carbon dioxide. This is a catabolic pathway but at the same time acetyl CoA can also be used in the biosynthesis of fatty acids (anabolic pathway). So, TCA cycle is also an amphibolic pathway.

Whereas, Calvin cycle is an anabolic pathway because it only involves the synthesis of glucose from carbon dioxide during photosynthesis. Hence, Calvin cycle is not an amphibolic pathway.