18.3 Oxidative Phosphorylation

Question 1

What is oxidative phosphorylation?

Answer 1

The process where the energy carried by electrons, from reduced coenzymes (reduced NAD, reduced FAD), is used to make ATP

Question 2

Describe and explain the stages in oxidative phosphorylation

Answer 2

1. Hydrogen atoms are released from NADH and FADH as they’re oxidised to NAD and FAD. The hydrogen atoms split into protons (H+) and electrons (e-)
2. The electrons move along the electron transport chain (made up of three electron carriers), losing energy at each carrier.
   The electron transport chain is located in the inner mitochondrial membrane.
   This membrane is folded into cristae, which increases the membrane’s surface area to maximise respiration.
3. This energy is used by the electron carriers to pump protons from the mitochondrial matrix into the intermembrane space (the space between the inner and outer mitochondrial membrane)
4. The concentration of protons is now high in the intermembrane space than in the mitochondrial matrix - this forms an electrochemical gradient
5. Protons move down the electrochemical gradient, back into the mitochondrial matrix, via ATP synthase
6. This movement drives the synthesis of ATP from ADP and inorganic phosphate
   This process of ATP production driven by the movement of H+ ions across a membrane is called chemiosmosis
7. In the mitochondrial matrix, at the end of the transport chain, the protons, electrons and oxygen (from the blood) combine to form water.
   Oxygen is said to be the final electron acceptor.

Question 3

Total number of ATP molecules formed from aerobic respiration

Answer 3

32 ATP