How many ATP molecules are produced per glucose in aerobic respiration?

~36-38 total: 2 from glycolysis + 2 from Krebs + ~32-34 from oxidative phosphorylation.

Why does fermentation yield so much less ATP than aerobic respiration?

Without O₂, the ETC can't run. NADH isn't oxidized, so only substrate-level phosphorylation in glycolysis yields 2 ATP.

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Cellular Respiration (Detailed)

Glycolysis, Krebs cycle, and oxidative phosphorylation step by step

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How it works

Cellular respiration converts glucose to ATP in three stages. Glycolysis (cytoplasm) splits glucose into 2 pyruvate, yielding 2 ATP and 2 NADH net. The Krebs cycle (mitochondrial matrix) oxidizes acetyl-CoA, producing 2 ATP, 6 NADH, and 2 FADH₂ per glucose. Oxidative phosphorylation (inner mitochondrial membrane) uses the electron transport chain to create a proton gradient, driving ATP synthase to produce ~32-34 ATP. Total yield: ~36-38 ATP per glucose. Without O₂, fermentation produces only 2 ATP per glucose (lactic acid or ethanol pathway).

Step-by-step

Watch glucose molecules pass through each stage.
The molecule counter tracks ATP, NADH, FADH₂, and CO₂ in real time.
Toggle oxygen to compare aerobic vs anaerobic respiration.

Key formulas

$\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \sim36\text{ATP}$ Overall aerobic respiration equation
$\text{Glycolysis: Glucose} \rightarrow 2\text{Pyruvate} + 2\text{ATP} + 2\text{NADH}$ Net products of glycolysis (cytoplasm)

Frequently asked questions

How many ATP molecules are produced per glucose in aerobic respiration?: ~36-38 total: 2 from glycolysis + 2 from Krebs + ~32-34 from oxidative phosphorylation.
Why does fermentation yield so much less ATP than aerobic respiration?: Without O₂, the ETC can't run. NADH isn't oxidized, so only substrate-level phosphorylation in glycolysis yields 2 ATP.