How NEET Tests 'Respiration' - High-Yield Traps

This is a numbers-and-sites chapter, and NEET rewards students who have the exact accounting. Master these rank-splitters:

  • Where each stage happens: glycolysis = cytoplasm; link reaction + Krebs cycle = mitochondrial matrix; ETS + oxidative phosphorylation = inner mitochondrial membrane.
  • Where CO2 is (and is NOT) released: NONE in glycolysis; first CO2 at the link reaction (pyruvate -> acetyl CoA); 2 CO2 per Krebs turn. Per glucose = 2 (link) + 4 (Krebs) = 6 CO2.
  • ATP accounting per glucose: substrate-level = 4 (2 net in glycolysis + 2 GTP in the Krebs cycle); oxidative phosphorylation = 34; total 38.
  • Reduced-coenzyme tally per glucose: glycolysis 2 NADH; link 2 NADH; Krebs 6 NADH + 2 FADH2. Total 10 NADH + 2 FADH2 -> (10x3)+(2x2) = 34 ATP by the ETS.
  • FADH2 gives only ~2 ATP (not 3) because it enters at ubiquinone via Complex II, bypassing Complex I. Complex II = succinate dehydrogenase, the single Krebs enzyme embedded in the inner membrane - it links the Krebs cycle to the ETS.
  • O2 is the terminal electron acceptor, used only at Complex IV, forming water; yet without it the entire chain halts. Per glucose, 6 O2 consumed.
  • Substrate-level vs oxidative phosphorylation: substrate-level makes ATP directly from a phosphorylated intermediate (glycolysis, Krebs GTP); oxidative phosphorylation uses the proton gradient + ATP synthase.
  • Fermentation: only 2 ATP; <7% of glucose energy; yeast -> ethanol + CO2, muscle -> lactic acid; NADH re-oxidised to NAD+.
  • RQ: carbohydrate = 1, fat < 1 (~0.7), protein ~0.9, organic acid > 1; pure anaerobic -> infinity.
  • Amphibolic pathway: respiratory intermediates are drawn off for biosynthesis (acetyl CoA -> fatty acids; ketoglutarate/OAA -> amino acids), so respiration is both catabolic and anabolic.

Below are challenging assertion-reason, match-the-column, multi-statement and sequence questions built on exactly these distinctions.