Topic 5: Energy transfers: Link Reactions

Link reactions

• sometimes called oxidative decarboxylation

• Takes place in the mitochondrial matrix

• Connects glycolysis (occurs in cytoplasm) to Krebs cycle, which occurs in the mitochondrial matrix

Steps of the link reaction

1. Active transport of pyruvate

2. Decarboxylation

3. Removal of carbon dioxide

4. Oxidation of pyruvate

5. Reduction of NAD

6. Formation of acetyl coenzyme A

Active transport of pyruvate

Pyruvate from glycolysis is actively transported into the mitochondrial matrix by specific carrier protein

Decarboxylation

In the mitochondrial matrix, each pyruvate molecule is decarboxylated, losing one molecule of carbon dioxide

Removal of carbon dioxide

Carbon dioxide diffuses out of the mitochondria as a waste product

Oxidation of pyruvate

Two hydrogen atoms are removed from pyruvate to form a two carbon molecule (acetate)

Reduction of NAD

The hydrogen atoms are used to reduce the coenzyme NAD, forming reduced NAD (an electron carrier)

Formation of acetyl coenzyme A

Acetate binds to coenzyme A, forming acetyl coenzyme A

Reactants

• Pyruvate

• NAD

• Coenzyme A

Products

• Acetyl coenzyme A

• Reduced NAD

• Carbon dioxide

Acetal coenzyme A delivers the acetyl group to the next stage of aerobic respiration,

Known as the Krebs cycle