Amphibolic Metabolic Pathway

Which of the following is an amphibolic (catabolic + anabolic) Pathway-

Correct Answer: Kreb's cycle

The Krebs cycle (TCA cycle) is the classic example of an amphibolic pathway — it serves both catabolic and anabolic functions simultaneously.

Why Krebs Cycle is Amphibolic?

• Catabolic role: Oxidizes Acetyl-CoA → CO₂ + H₂O + energy (as NADH, FADH₂, GTP)
• Anabolic role (anaplerosis): Intermediates feed into synthesis of:
  • Amino acids: α-ketoglutarate → glutamate; oxaloacetate → aspartate
  • Glucose: oxaloacetate → gluconeogenesis
  • Fatty acids: citrate exported → cytoplasm → lipogenesis
  • Heme: succinyl-CoA → heme synthesis

Pathway Classification

• Catabolic only: Glycolysis, β-oxidation of fatty acids
• Anabolic only: Gluconeogenesis, Lipogenesis, Protein synthesis
• Amphibolic (both): Krebs cycle

Memory Tip

Amphibolic = Amphi (both sides) + bolic (metabolism). Like an amphibian living on both land and water, Krebs cycle works in both metabolic directions.