Question

What is the role of O₂ in respiration and how is ATP synthesized?

Answer 1

Oxidative phosphorylation:

1. Oxygen is required for oxidative phosphorylation, which takes place in the mitochondria and leads to the synthesis of most of the ATP produced during cellular respiration.
2. Oxidative phosphorylation comprises an electron transport chain, which generates the proton gradient across the inner mitochondrial membrane and chemiosmosis that drives the ATP synthesis by ATP synthase.
3. When NADH and FADH₂ produced in the earlier steps of cellular respiration are oxidized, the electrons pass from complex I to IV in the electron transport chain, and protons are pumped from the matrix to intermembrane space using the energy released from electrons.
4. Oxygen molecules act as a final hydrogen acceptor. This generates the proton gradient that is utilized in ATP synthesis.
5. ATP synthase (complex V) contains two subunits, F0, the integral membrane protein, and F1, the peripheral protein.
6. F0 forms the channel through which protons pass the inner membrane. This is coupled with the catalysis by F1 to produce ATP from ADP and Pi.
7. For every ATP produced, two protons across the inner membrane from intermembrane space to the matrix through F0 down the proton gradient.
8. As the energy for phosphorylation is derived from oxidation-reduction reactions, it is called oxidative phosphorylation.

Diagram of oxidative phosphorylation is given below: