ATP Yield from Cellular Respiration
Calculate ATP produced from glucose metabolism.
Compare aerobic respiration (32 ATP) versus anaerobic glycolysis (2 ATP) with a stage-by-stage breakdown chart.
Cellular respiration converts glucose into ATP (adenosine triphosphate), the universal energy currency of cells. The pathway used determines how much ATP is produced.
Aerobic respiration (requires oxygen) proceeds through three stages:
Glycolysis breaks one glucose molecule into two pyruvate molecules in the cytoplasm. Net yield: 2 ATP + 2 NADH. No oxygen required. This is the same starting point for both aerobic and anaerobic pathways.
Pyruvate oxidation and the Krebs cycle (citric acid cycle) process the two pyruvates in the mitochondria. Substrate-level phosphorylation yields 2 ATP, plus 8 NADH and 2 FADH2, which carry high-energy electrons to the next stage.
Oxidative phosphorylation (electron transport chain) uses those electron carriers to pump protons across the inner mitochondrial membrane, driving ATP synthase. Modern P/O ratios give approximately 2.5 ATP per NADH and 1.5 ATP per FADH2. Total: 10 NADH x 2.5 + 2 FADH2 x 1.5 = 28 ATP.
Aerobic total: 2 + 2 + 28 = 32 ATP per glucose (modern estimate; older textbooks cite 36-38).
Anaerobic respiration (glycolysis only) produces just 2 ATP per glucose. Pyruvate is converted to lactate (in animals) or ethanol + CO2 (in yeast) to regenerate NAD+ and keep glycolysis running. This is why sprinting muscles fatigue quickly while a resting heart beats for decades.
The 16-fold difference in yield explains why aerobic organisms sustain dramatically higher activity levels.