4.3 Electron transport chain

Question 1

Electron transport chain

Occurs in?
What phosphorylation?
Importance of cristae?
Metabolically active cells have? (2)

Answer 1

4.3 Electron transport chain
Mitochondrial matrix
Oxidative phosphorylation
contains coenzymes
-More mitochondria
-More densely packed cristae - greater surface area

Question 2

Process (6)

1. Reduced coenzymes…
2. Protons…
3. Electrons… (2)
4. Protons…
5. At end of chain…

Answer 2

1. Reduced coenzymes from Krebs cycle donate electrons to first carrier molecule in ETC
2. Protons actively transported between 2 mitochondrial membranes and accumulate.
3. Electrons pass along ETC in series of oxidation-reduction reactions losing energy along way:
   - Some used to combine ADP+Pi = ATP
   - Some released as heat
4. Protons diffuse back into matrix through protein channels.
5. At end of chain electrons combine with protons and oxygen (final electron acceptor) to form water.

Question 3

Why is oxygen important?

Without it? (2)

Answer 3

Acts as final electron acceptor

• Electrons and protons would ‘back up’/accumulate on chain
• Respiration would stop.

Question 4

Describe and explain effect of cyanide on ETC (3)

Answer 4

1. Non-competitive inhibitor of final electron carrier
2. Combination of electrons, protons and oxygen into water not catalysed
3. Respiration stops