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Question

Oxidative phosphorylation

Answer 1

Oxidative phosphorylation is a key metabolic pathway in cellular respiration, primarily occurring in the mitochondria. It is the process by which cells generate ATP (adenosine triphosphate), the energy currency of the cell, through the transfer of electrons from nutrients to oxygen.

Here’s a breakdown of the process:

1. Electron Transport Chain (ETC):

   • The process begins with high-energy electrons derived from NADH and FADH2 (produced earlier in glycolysis and the citric acid cycle). These electrons are transferred through a series of protein complexes (I, II, III, IV) embedded in the inner mitochondrial membrane.
   • As the electrons move through these complexes, energy is released and used to pump protons (H⁺) across the inner mitochondrial membrane, creating a proton gradient (higher concentration of H⁺ in the intermembrane space).

2. Proton Gradient and Chemiosmosis:

   • The proton gradient creates a potential energy difference (proton motive force) across the membrane.
   • Protons flow back into the mitochondrial matrix through a protein called ATP synthase. As protons pass through ATP synthase, the energy is harnessed to combine ADP and inorganic phosphate (Pi) to form ATP.

3. Final Electron Acceptor:

   • The electrons, after passing through the ETC, ultimately combine with protons and molecular oxygen (O₂) to form water (H₂O). Oxygen acts as the final electron acceptor, which is why oxygen is essential for this process.

Key Points:

• Oxidative phosphorylation produces the majority of ATP in aerobic cells (approximately 30-34 ATP molecules per molecule of glucose).
• It occurs in the inner mitochondrial membrane and involves both the electron transport chain and ATP synthesis driven by proton movement.
• It is an aerobic process, requiring oxygen to function.

This process is vital for energy production in most eukaryotic cells and is closely linked to cellular respiration.