1. Key Area 2b Electron Transport Chain
Metabolism & Survival
Key Area 2b
Electron Transport Chain

2. By the end of this topic you should be able to:
Describe how ATP is synthesised

3. Electron Transport Chain
This is the third stage of aerobic respiration.
Electrons are passed along the ETC releasing energy
The hydrogen (attached to its carrier NAD to make NADH) and electrons combine with oxygen to make water and produce ATP.
The Electron Transport Chain takes place on the cristae of the mitochondria

4. The Electron Transport Chain
The ETC is a series of carrier proteins attached to the inner mitochondrial membrane
All the Hydrogen ions and electrons that have been transferred to NAD are passed to the ETC.
Within the ETC the H ions and electrons now separate, with the electrons cascading down the ETC and releasing their energy

5. The Electron Transport Chain
The energy from the electrons are used to pump Hydrogen ions across the inner mitochondrial membrane.
The flow of these ions back through the membrane protein ATP Synthase results in the production of ATP

6. The Electron Transport Chain

7. The Electron Transport Chain
NADH from glycolysis and the citric acid cycle release electrons and pass them to the electron transport chains.

8. As the electrons flow along a chain of carrier proteins, they release energy.
This energy is used to pump hydrogen ions across the membrane (active transport) from the matrix side to the inter-membrane space to maintain a higher concentration of hydrogen ions.

9. When the hydrogen ions flow back down the concentration gradient to the matrix they pass through the membrane protein ATP synthase.
This drives the synthesise ATP from ADP and Pi.

10. Finally, the hydrogen ions and electrons combine with oxygen to form water

11. Why is oxygen needed?
Oxygen is the final electron and hydrogen acceptor and without it the ETC cannot function!
Hydrogen is an explosive gas and is very reactive acidic ion so it must also combine with oxygen
½ O2 + 2e- + 2H H2O