Question

During which stage in the complete oxidation of glucose are the greatest number of ATP molecules formed from ADP?

• A. Kreb’s cycle
• B. Glycolysis
• C. Electron transport chain
• D. Conversion of pyruvic acid to acetyl CoA

Hint:

Maximum ATP production during respiration occurs in the \textbf{Electron Transport Chain} via oxidative phosphorylation.

Answer 1

The Correct Option is C

Step 1: The complete oxidation of glucose occurs in four main stages:

Glycolysis
Conversion of pyruvic acid to acetyl CoA
Krebs cycle
Electron Transport Chain (ETC)

Step 2: Glycolysis and Krebs cycle produce only a small number of ATP molecules by substrate-level phosphorylation.
Step 3: Most of the reduced coenzymes (NADH and FADH$_2$) are formed during glycolysis, pyruvate oxidation, and Krebs cycle.
Step 4: These reduced coenzymes donate electrons to the Electron Transport Chain, where a large proton gradient is created across the inner mitochondrial membrane.
Step 5: ATP synthase uses this proton gradient to synthesize the maximum number of ATP molecules from ADP by oxidative phosphorylation.