Which pathway in cellular respiration generates the most ATP?

Correct — C. Using NCERT's figures, with glycolysis NADH taken into the mitochondria:

Glycolysis: net 2 ATP, plus 2 NADH
Link reaction and Krebs cycle: 2 ATP, 8 NADH, 2 FADH₂

Electron transport: 10 NADH × 3 = 30, and 2 FADH₂ × 2 = 4
Chain total = 34 of the 38 ATP → option (c)

Why the others are wrong

• (a)
  Glycolysis — Glycolysis nets only 2 ATP per glucose, in the cytoplasm. Its bigger contribution is 2 NADH, whose energy is cashed in later by the electron transport chain.
• (b)
  Krebs cycle — The Krebs cycle makes just 2 ATP per glucose directly. Its real output is NADH and FADH₂, which yield ATP only when the electron transport chain oxidises them.
• (d)
  Fermentation — Fermentation nets only 2 ATP per glucose, all from glycolysis, and NCERT notes it releases less than seven per cent of the energy in glucose.

Aerobic respiration runs in three stages: glycolysis in the cytoplasm, the Krebs cycle in the mitochondrial matrix, and the electron transport system on the inner mitochondrial membrane.

The first two stages mostly strip electrons from glucose and load them onto NADH and FADH₂. In the third, those electrons pass along complexes I to IV to oxygen, the final hydrogen acceptor, and ATP synthase uses the energy released to make ATP.

That coupling is oxidative phosphorylation.

Key facts

• The electron transport system sits on the inner mitochondrial membrane, with oxygen as the final hydrogen acceptor.
• In NCERT's count, one NADH yields 3 ATP and one FADH₂ yields 2 ATP.
• NCERT puts the net gain from aerobic respiration of one glucose at 38 ATP.
• Fermentation nets only 2 ATP per glucose.

Common traps

• Crediting the Krebs cycle with the ATP, when it mainly produces NADH and FADH₂ for the chain.
• Counting fermentation as a separate ATP source, when its 2 ATP come from glycolysis.

No directly related past PYQ was found.