Aerobic Respiration

Question 1

In aerobic respiration how does pyruvate enter the mitochondrial matrix?

Answer 1

active transport

Question 2

What happens after the pyruvate enters the mitochondrial matrix?

Answer 2

The Link reaction

Question 3

Summerise the link reaction

Answer 3

1. a carboxyl group is removed from pyruvate, releasing CO2
2. NAD+ is reduced to NADH
3. an acetyl group is transferred to coenzyme A, resulting in acetyl CoA

Question 4

What is the point of the link reaction?

Answer 4

At the end of glycolysis, we have two pyruvate molecules that still contain lots of extractable energy.
Pyruvate oxidation is the next step in capturing the remaining energy in the form of ATP although no ATP is made directly during pyruvate oxidation.

Question 5

The outcome of the link reaction is …

Answer 5

Two molecules of pyruvate are converted into two molecules of acetyl CoA
Two carbons are released as carbon dioxide—out of the six originally present in glucose.
2 NADH are generated from NAD+

Question 6

What occurs after the link reaction?

Answer 6

The Krebs cycle

Question 7

Stage 1 of the Krebs cycle

Answer 7

1. Acetyl CoA delivers an acetyl group to the Krebs cycle

2. the 2-carbon acetyl group combines with the 4-carbon (oxaloacetate) to form 6-carbon (citrate)

Question 8

Stage 2 of the Krebs cycle

Answer 8

1. The citrate (6c) undergoes decarboxylation and dehydrogenation to produce 1 NAD, CO2 and a 5C compound.

Question 9

Stage 3 of the Krebs cycle

Answer 9

1. 5C compound undergoes further decarboxylation and dehydrogenation eventually regenerating oxaloacetate
2. CO2, NAD and reduced FAD are produced

Question 10

How is ATP generated during the kerbs cycle?

Answer 10

substrate-level phosphorylation

Question 11

What happens after the Krebs cycle?

Answer 11

oxidative

phosphorylation

Question 12

What happens in oxidative phosphorylation? (part 1)

stages 1 and 2

Answer 12

1. Reduced NAD and FAD donate electrons to the electron transfer chain in the inner mitochondrial membrane.
2. The release of energy as the electrons pass down the electron
   transfer chain is used to create a proton gradient across the inner mitochondrial membrane into the inter-membranal space.

Question 13

What happens in oxidative phosphorylation? (part 2)

stages 3 and 4

Answer 13

3. The proton gradient is used to synthesis ATP by oxidative phosphorylation, catalysed by ATP synthase (chemiosmotic
   theory).
4. Oxygen combines with the protons that have dif used through the ATP synthase channel and the electrons that have been
   passed along the electron transfer chain, acting as the final electron acceptor.

Question 14

Why is a final electron acceptor important in oxidative phosphorylation?

Answer 14

to maintain the proton gradient for the

electron transfer chain to continue.

Question 15

Aerobic vs Anaerobic ATP production

Answer 15

Aerobic respiration produces 32 ATP. 30 more than anaerobic respiration.

Question 16

Apart from sugars what else can be a respiratory substrate?

Answer 16

Lipids and carbohydrates

Lipids release more energy than carbohydrates, due to more carbon-hydrogen bonds

Question 17

Lipids significance in respiration

Answer 17

1. Hydrolysed to fatty acids and glycerol.
2. Glycerol is phosphorylated and converted to triose
   phosphate, which enters the glycolysis pathway
3. The fatty acid part is broken down into 2-carbon
   fragments which are subsequently converted into
   acetyl CoA, also generating reduce NAD & FAD

Question 18

Proteins significance in respiration

Answer 18

1. Protein is hydrolysed to amino acids. - In the liver, the amino group is removed (deamination), and the amino group is converted to urea and removed in the urine.
2. The remaining amino acid can then be converted to an
   intermediate

Question 19

How would you know if anaerobic respiration was occurring?

Answer 19

The respiratory quotient (RQ) is greater than 1

Question 20

How do you calculate the respiratory quotient (RQ)?

Answer 20

CO2 produced / O2 produced