Oxidative phosphorylation is the process in cells where ATP (energy currency of the cell) is made using oxygen.
- It happens in the mitochondria (the “powerhouse” of the cell).
- It combines oxidation (electron transfer) with phosphorylation (adding phosphate to ADP → ATP).
How Does It Work?
- Electron Transport Chain (ETC)
- High-energy electrons come from molecules like NADH and FADH₂ (produced in glycolysis and Krebs cycle).
- These electrons move through a chain of proteins in the inner mitochondrial membrane.
- As they move, protons (H⁺ ions) are pumped across the membrane, creating a proton gradient.
- Oxygen as Final Electron Acceptor
- At the end of the chain, electrons combine with oxygen and hydrogen to form water.
- This is why oxygen is essential for life!
- ATP Synthase (Energy Machine)
- The proton gradient (like stored water behind a dam) flows back through an enzyme called ATP synthase.
- This movement provides the energy to convert ADP + Pi → ATP.
End Result
- About 34 ATP molecules are produced from one glucose (the biggest energy yield in respiration).
- By contrast, glycolysis makes only 2 ATP.
Why is it Important?
- Provides the main source of energy for cells.
- Powers all cellular activities (muscle contraction, nerve signals, biosynthesis, etc.).
- Explains why we need oxygen to survive.
In short:
Oxidative phosphorylation is the final stage of cellular respiration where cells use oxygen and electrons from food to make lots of ATP (energy) in the mitochondria.