5.7.5 The Link reaction

Question 1

What is the end product of glycolysis?

Answer 1

Pyruvate

Question 2

What does pyruvate contain and why is it useful?

Answer 2

A substantial amount of chemical energy that can be further utilised in respiration to produce more ATP

Question 3

What happens to pyruvate when oxygen is present?

Answer 3

When oxygen is available, pyruvate will enter the mitochondrial matrix and aerobic respiration will continue.

Pyruvate moves across the double membrane of the mitochondria via active transport - therefore requires a transport protein and a small amount of ATP.

Question 4

How does pyruvate cross the double membrane of the mitochondria?

Answer 4

By active transport, and therefore requires a transport protein and a small amount of ATP

Question 5

Why is it called the link reaction?

Answer 5

As it links glycolysis to the Krebs cycle

Question 6

What are the steps of the link reaction?

Answer 6

1. Pyruvate is oxidised by enzymes to produce acetate CH3CO(O)- and carbon dioxide, requiring the reduction of NAD to NADH
2. Combination of coenzyme A to form acetyl coenzyme A

Question 7

What does the link reaction produce?

Answer 7

• Acetyl coA
• CO2
• NADH

Question 8

What is coenzyme A

Answer 8

A molecule that helps an enzyme carry out its function but its not used in the reaction itself.

Question 9

What does coenzyme A consist of?

Answer 9

Nucleoside (ribose and adenine) and a vitamin

Question 10

What does CoA do in the link reaction?

Answer 10

It binds to the remainder of the pyruvate molecule (acetyl group 2C) to form acetyl coA
- It then supplies the acetyl group to the Krebs cycle where it is used to continue aerobic respiration

Question 11

How many molecules of pyruvate are produced from a single glucose molecule in aerobic respiration?

Answer 11

2
Therefore you need to multiply everything by 2 when thinking about what happens to a single glucose molecule in aerobic respiration