Cell respiration

Science

Definition

Cellular respiration is the metabolic process by which cells break down glucose and other organic molecules to produce ATP, the cell's main energy currency. It occurs in three main stages and primarily takes place in the mitochondria.

How It Works

  1. Glycolysis splits one glucose molecule into two pyruvate molecules in the cytoplasm, producing 2 ATP and 2 NADH.
  2. Pyruvate is oxidized and enters the Krebs cycle in the mitochondrial matrix, generating CO2, NADH, FADH2, and 2 ATP.
  3. The electron transport chain on the inner mitochondrial membrane uses NADH and FADH2 to create a proton gradient.
  4. Oxidative phosphorylation uses the proton gradient to drive ATP synthase, producing about 30-34 ATP.
  5. Oxygen serves as the final electron acceptor, combining with electrons and hydrogen ions to form water.

Examples

  • Your muscle cells ramp up cellular respiration during exercise to meet energy demands
  • Yeast cells switch to fermentation (anaerobic respiration) when oxygen is unavailable, producing alcohol
  • Every cell in your body performs cellular respiration 24/7 to maintain life functions
Key Fact

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ~36-38 ATP

Related Terms

Photosynthesis Atp cycle Enzyme structure Cell organelles

Study This Concept

Practice cell respiration with free review games in these units:

AP Biology Unit 3: Cellular Energetics