Stages of cellular respiration: glycolysis, Krebs and electron transport

How the cell gets ~36 ATP from one glucose, step by step. The three stages, where they occur and how much energy each yields.

Direct answer: Cellular respiration has 3 stages: glycolysis (in the cytoplasm; glucose → 2 pyruvate, +2 ATP), the Krebs cycle (in the mitochondrial matrix; releases CO₂ and NADH/FADH₂) and the electron transport chain (on the mitochondrial cristae; uses O₂ and produces most of the ATP, ~34).

Table of the 3 stages

Stage	Where	Produces
Glycolysis	Cytoplasm	2 pyruvate, 2 ATP, 2 NADH
Krebs cycle	Mitochondrial matrix	CO₂, NADH, FADH₂, 2 ATP
Electron transport chain	Cristae (inner membrane)	~34 ATP, H₂O

Approximate total yield: ~36–38 ATP per glucose. The final electron acceptor is oxygen.

Exam trap: most of the ATP is produced in the electron transport chain (oxidative phosphorylation), not in glycolysis. Without oxygen, the cell resorts to fermentation and gets far less ATP.

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Frequently asked questions

What are the stages of cellular respiration?

Glycolysis, the Krebs cycle and the electron transport chain.

Where does each stage occur?

Glycolysis in the cytoplasm; Krebs in the mitochondrial matrix; the electron transport chain on the mitochondrial cristae.

How much ATP is produced in total?

Approximately 36–38 ATP per glucose molecule.