5.1.4 - Link reaction and Krebs cycle

Question 1

What does the link reaction do?

Answer 1

The link reaction links glycolysis in the cytoplasm with the Krebs cycle in the mitochondria (matrix of mitochondria).
Glucose is too large and there are no transport
proteins to allow it to enter the mitochondria.
The link reaction allows this to happen

Question 2

What is the name of the compound that begins the link reaction?

Answer 2

Pyruvate

Question 3

What happens to pyruvate at the start of the link reaction?

Answer 3

It loses a carbon in the form of carbon dioxide.

Question 4

How does the pyruvate molecule move into the mitochondria?

Answer 4

Active transport.

Question 5

What happens to the 2-carbon fragment that is produced when pyruvate releases a CO2 molecule in the link reaction?

Answer 5

It is oxidised and so then NAD is reduced to form NADH.

Question 6

What is the end product of the link reaction?

Answer 6

Acetyl Coenzyme A

Question 7

How many carbons does acetyl CoA contain?

Answer 7

2

Question 8

What is the first stage of the Krebs cycle?

Answer 8

Acetyl CoA from the link reaction is broken down into acetate.
CoA is removed.

Question 9

What happens to acetate in the krebs cycle?

Answer 9

Joins with oxaloacetate (4 carbon molecule)

Question 10

What is formed when acetate and oxaloacetate join?

Answer 10

Citrate
(6 carbon molecule)

Question 11

What happens to citrate when it is formed in the Krebs cycle?

Answer 11

It is decarboxylated to form alpha ketogluterate
(5 carbon molecule)

Question 12

What is the net formation of products from a krebs cycle of one acetate CoA?

Answer 12

1 FADH2
3 NADH
1 ATP
2CO2

Question 13

What happens when citrate is oxidised?

Answer 13

It reduces a NAD molecule to form NADH

Question 14

Explain the role of the Krebs cycle.

Answer 14

Completely oxidises Acetyl CoA.
To release as much energy as possible.
To produce NADH.
So therefore ATP can be produced in the electron transport chain.