Q.41 The net number of molecule(s) of NADH formed from one molecule of glucose in
glycolysis under aerobic conditions is/are _______.

Net NADH molecules from one glucose in glycolysis under aerobic conditions is 2.​

Glycolysis produces exactly 2 NADH per glucose molecule regardless of oxygen availability, as the NADH arises solely from the glyceraldehyde-3-phosphate dehydrogenase step. Under aerobic conditions, these NADH molecules shuttle electrons to mitochondria via shuttles like malate-aspartate, but the net count formed in glycolysis remains unchanged. This holds true in standard biochemistry for CSIR NET Life Sciences preparation.​

One glucose molecule yields a net of 2 NADH molecules during glycolysis, even under aerobic conditions. This key fact appears frequently in CSIR NET Life Sciences exams testing metabolic pathway outputs. Understanding NADH production helps distinguish glycolysis from full cellular respiration totals.​

Glycolysis NADH Steps

Glycolysis splits glucose (C6) into two pyruvate (C3) via 10 enzyme steps in cytosol. NADH forms only in step 6: glyceraldehyde-3-phosphate (G3P) oxidizes to 1,3-bisphosphoglycerate by G3P dehydrogenase, reducing NAD⁺ to NADH. Since glucose yields two G3P, total gross NADH is 2; no NADH consumes in glycolysis, so net is 2.​

• No NADH in preparatory phase (steps 1-5: uses 2 ATP).

• Payoff phase (steps 6-10): produces 4 ATP + 2 NADH.

• Aerobic conditions do not alter this; NADH later enters mitochondria.​

Aerobic vs Anaerobic

Under aerobic conditions, pyruvate enters mitochondria, and glycolysis NADH regenerates NAD⁺ via shuttles (malate-aspartate yields ~2.5 ATP/NADH; glycerol-phosphate ~1.5 ATP/NADH). Anaerobic: NADH reduces pyruvate to lactate (or ethanol in yeast), regenerating NAD⁺ cytosolically. Net NADH formed stays 2 in both; difference is fate, not production.​

Common Exam Confusions

Tricky options often test total respiration NADH (10 from glycolysis + pyruvate oxidation + TCA) or ATP equivalents (glycolysis NADH ~5 ATP aerobically). Focus: question specifies “formed … in glycolysis,” so 2. No options given, but typical fill-in expects “2”.​

For CSIR NET, memorize: glycolysis net = 2 ATP + 2 NADH per glucose, universal across conditions.​