Mitochondria + the link reaction

What is the purpose of the intermembrane space?

• protons are pumped into the space by the ETC

• space is small so the concentration builds up quickly

What is the purpose of the matrix?

• contains enzymes for the krebs cycle and the link reaction

• also contains mitochondrial DNA

• has a suitable pH

What is the purpose of the inner membrane?

• contains ETC and ATP synthase

• for oxidative phosphorylation

What is the purpose of the cristae?

• increases SA:vol ratio

• are projections of the inner membrane which increase SA available for oxidative phosphorylation

What is the purpose of the outer membrane?

• separates the contents of the mitochondrion from the rest of the cell

• creates cellular compartment with ideal conditions for aerobic respiration

• contains transport proteins for shuttling pyruvate into mitochondrion

What happens in the link reaction?

pyruvate (3C) is converted to acetate (2C)

Where does the link reaction occur?

In the mitochondrial matrix

How is pyruvate transported to the mitochondrial matrix?

Actively transported across the outer and inner membranes

What is another name for the link reaction?

oxidative decarboxylation

What are the steps of the link reaction?

1. decarboxylation of a pyruvate molecule

2. oxidation of pyruvate molecule

3. remaining 2C molecule combines with coenzyme A to produce acetyl CoA

What happens in the first step of the link reaction?

Decarboxylation

• one carbon atom is removed from pyruvate

• this form CO₂

What is the enzyme need to remove a carbon from pyruvate in the link reaction?

pyruvate decarboxylase

What happens in the second step of the link reaction?

Oxidation

• hydrogen is removed from pyruvate

• it is accepted by NAD to form NADH

What enzyme is needed to oxidise pyruvate in the link reaction?

pyruvate dehydrogenase

What happens in the third step of the link reaction?

• remaining 2C molecule = acetate

• it combines with coenzyme A

• forms acetyl coenzyme A

Is ATP produced in the link reaction?

No

What does acetyl CoA do after being produced in the link reaction?

delivers the acetyl group into the Krebs cycle

How many times does the link reaction occur per glucose molecule?

• 2x per molecule

• because there are 2 pyruvate produces per glucose in glycolysis

What is used in the link reaction?

• 2 pyruvate

• 2 NAD

• 2 CoA

What is produced in the link reaction?

• 2CO₂

• 2 NADH

• 2 acetyl CoA