Q63.ATP molecules produced by oxidation of one molecule of palmitoyl-CoA to CO₂ and H₂O are
(1) 38
(2) 108
(3) 148
(4) 40
Palmitoyl-CoA Oxidation: ATP Yield Explained
Complete oxidation of one palmitoyl-CoA molecule (derived from palmitic acid, C16) through beta-oxidation and the citric acid cycle produces 108 ATP molecules.
Correct Answer
Option (2) 108 represents the total ATP yield for palmitoyl-CoA oxidation to CO₂ and H₂O.
This accounts for 7 beta-oxidation cycles yielding 7 NADH, 7 FADH₂, and 8 acetyl-CoA, with modern ATP equivalents of ~2.5 per NADH and ~1.5 per FADH₂, plus 10 ATP per acetyl-CoA.
Option Breakdown
Beta-Oxidation ATP Calculation
Palmitoyl-CoA (C16) undergoes 7 cycles: each produces 1 NADH (~2.5 ATP), 1 FADH₂ (~1.5 ATP), and cleaves 1 acetyl-CoA (10 ATP via TCA/ETC).
Final cycle yields 2 acetyl-CoA, totaling 8 acetyl-CoA (80 ATP), 7 NADH (17.5 ATP), 7 FADH₂ (10.5 ATP).
Note: Activation to palmitoyl-CoA costs 2 ATP equivalents (ATP → AMP + PPi), yielding net 106 ATP for free palmitic acid—not asked here.
Why Variations Exist
Older texts use 3 ATP/NADH and 2 ATP/FADH₂ (yielding ~129-131 gross), but proton leak and transport costs reduce to ~2.5/1.5 in eukaryotes.
