The Link Reaction
Entering the link reaction
- The end product of glycolysis is pyruvate (3C)
- Pyruvate contains a substantial amount of chemical energy that can be further utilised in respiration to produce more ATP
- When oxygen is available pyruvate will enter the mitochondrial matrix and aerobic respiration will continue
- Once in the matrix pyruvate takes part in the link reaction
The link reaction
- The link reaction takes place in the matrix of the mitochondria
- It is referred to as the link reaction because it links glycolysis to the Krebs cycle
- The steps are:
- Oxidative decarboxylation reaction in which:
- Carbon dioxide is removed to produce a 2C molecule
- This 2C molecule is then oxidised (loss of hydrogen and 2 high energy electrons) to produce an acetyl compound and thereby reducing NAD to NADH
- Combination of the acetyl compound with coenzyme A to form acetyl coenzyme A (acetyl CoA)
- Oxidative decarboxylation reaction in which:
- It produces:
- Acetyl CoA
- Carbon dioxide (CO2)
- Reduced NAD (NADH)
pyruvate + NAD + CoA → acetyl CoA + carbon dioxide + reduced NAD
- Acetyl coenzyme A is supplied to the Krebs cycle where aerobic respiration continues
Link Reaction Diagram
The link reaction occurs in the mitochondrial matrix. It dehydrogenates and decarboxylates the three-carbon pyruvate to produce the two-carbon acetyl CoA that can enter the Krebs Cycle.
Examiner Tip
Remember that there are two pyruvate molecules produced per glucose molecule so you need to multiply everything by 2 when thinking about what happens to a single glucose molecule in aerobic respiration.