- A Citrate combining with NADH to form isocitrate
- B Acetyl CoA combining with oxaloacetate to form citrate
- C Pyruvate combining with CO2 to form oxaloacetate
- D Succinyl CoA combining with fumarate to form malate
Correct answer: B. Acetyl CoA combining with oxaloacetate to form citrate
Explanation: The Krebs cycle begins when the 2-carbon acetyl CoA combines with the 4-carbon oxaloacetate to form the 6-carbon citrate, catalyzed by citrate synthase.
Concept context
Glycolysis, the Krebs cycle, the electron transport chain, fermentation, and the respiratory quotient. The cellular energy-release counterpart to photosynthesis.