Q.In eucaryotes the complete oxidation of a molecule of glucose results in the net gain of

Step 1. Recall the balance-sheet totals. Table 13.3 tallies ATP production across all three ATP-generating stages of aerobic respiration: glycolysis (net 8 ATP after its own 2-ATP investment), the conversion of 2 pyruvate to 2 acetyl-CoA (6 ATP, from 2 NADH+H⁺), and the Krebs cycle turning twice per glucose (24 ATP, from 2 GTP plus 6 NADH+H⁺ and 2 FADH₂).

Step 2. Sum the totals. Substrate-level phosphorylation contributes 2 (glycolysis) + 2 (Krebs cycle) = 6 ATP; oxidative phosphorylation contributes 6 (glycolysis NADH) + 6 (link-reaction NADH) + 18 (Krebs NADH) + 4 (Krebs FADH2) = 34 ATP. Gross total = 6 + 34 = 40 ATP.

Step 3. Subtract the ATP invested. Glycolysis itself spends 2 ATP in its preparatory phase, so the net gain is 40 - 2 = 38 ATP.

Summing Table 13.3's step-by-step ATP tally (substrate-level + oxidative phosphorylation across glycolysis, the link reaction, and the Krebs cycle) and subtracting the 2 ATP consumed in glycolysis

• Quoting the gross total (40) instead of the net benefit (38) that the question actually asks for.
• Confusing this book's own net figure (38) with the alternative 36-ATP convention used by some other textbooks, which deducts extra ATP for shuttling cytoplasmic NADH across the mitochondrial membrane.