3.5.2.2 - Oxidative Phosphorylation (ETC)

Question 1

Where does oxidative phosphorylation occur?

Answer 1

Cristae/inner membrane of mitochondria

Question 2

Describe the process of oxidative phosphorylaiton (chemiosmotic theory) within the mitochondria.

Answer 2

1. NADH/FADH₂ release electrons.
2. Electrons taken up by ETC via a series of redox reactions.
3. Electrons give energy to proton pumps in ETC.
4. Protons are pumped into intermembrane space creating an electrochemical gradient.
5. Protons move through ATP synthase
6. This catalyses ADP+Pi –> ATP
7. Electrons from ETC move to oxygen (final electron acceptor)

Question 3

Why is oxygen so important to aerobic respiration.

Answer 3

It is the final electron acceptor.

H+ and electron transport would stop.

NAD and FAD cannot be resynthesised as NADH and FADH₂ cannot give up their H+ and electrons.

Question 4

The energy not harvested during the electron transport chain is lost as…

Answer 4

heat

Question 5

The enzyme that catalyses the reaction of ADP + Pi –> ATP is…

Answer 5

ATP synthase

Question 6

Many mitochondria are present in metabolically active cells such as…

Answer 6

Muscle (contraction)

Liver (detoxification)

Epithelial cells (secretion)

Question 7

The mitochondria of metabolically active cells have more densley packed cristae. How does this help these cells?

Answer 7

A greater surface area of inner membrane is provided which include the enzymes and proteins involved in oxidative phosphorylation.

Question 8

Why is it more useful to release energy in stages via an electron transport chain rather than all at once in one single step?

Answer 8

The transfer of electrons down an energy gradient allows energy to be released in a more gradual way.

This minimises energy wasted as heat.