Aerobic Respiration

Question 1

Where does the link reaction occur?

Answer 1

• The mitochondrial matrix.

Question 2

Link reaction.

Answer 2

• Pyruvate is decarboxylated.
• Pyruvate is oxidised to form acetate and NAD and is reduced to form reduce NAD.
• Acetate is combined with CoA, to form acetyl CoA.

Question 3

How many ATP molecules are produced in the link reaction?

Answer 3

• None.

Question 4

How many times does the link reaction occur for every glucose molecule?

Answer 4

• Twice.

Question 5

Krebs cycle.

Answer 5

1. Acetyl CoA from the LR combines with oxaloacetate to form citrate.
   CoA goes back into the LR.
2. 6C citrate molecule converted to 5C molecule.
   Decarboxylation occurs.
   Dehydrogenation occurs.
   The H is used to produce reduced NAD.
3. 5C molecule converted to 4C molecule.
   Decarboxylation and dehydrogenation occurs, producing 1 molecule of reduced FAD and 2 of reduced NAD.
   ATP is produced by direct transfer of phosphate group from intermediate compound to ADP.
   Citrate has been converted into oxaloacetate.

Question 6

Where does the Krebs cycle happen?

Answer 6

• In the matrix of the mitochondria.

Question 7

How many times does the Krebs cycle happen per pyruvate molecule?

Answer 7

• Once.

Question 8

How many times does the Krebs cycle happen per glucose molecule?

Answer 8

• Twice.

Question 9

Where does oxidative phosphorylation happen?

Answer 9

• Across the mitochondrial membrane.

Question 10

Oxidative phosphorylation.

Answer 10

1. H ions released from reduced NAD and reduced FAD. H ions split into protons and electrons.
2. Electrons move down ETC, losing energy at each carrier.
3. This energy is used to pump protons from matrix into intermembrane space.
4. Concentration of protons is now higher in the intermembrane space, forming an electrochemical gradient.
5. Protons move down gradient via ATP synthase, ATP is synthesised from ADP and Pi.
6. At the end of transport chain, protons, electrons and O2 combine to form water. Oxygen is the final electron acceptor.

Question 11

How can ATP production be affected?

Answer 11

• By mitochondrial diseases.

Question 12

How do mitochondrial diseases affect ATP production?

Answer 12

• Reduce ATP production.
• May cause anaerobic respiration to increase, to make up for ATP shortage.
• Results in lots of lactate being produced, causing muscle fatigue and weakness.
• Some lactate will diffuse into bloodstream, leading to high lactate concentrations in the blood.