The Link Reaction

what happens to the pyruvate molecule produced from glycolysis

ACTIVELY transported from cytoplasm into mitochondrial matrix and take part in link reaction

Describe how pyruvate enters the mitochondrial matrix from the cytoplasm.

• Via active transport [1]

• Using specific carrier proteins spanning the inner and outer mitochondrial membranes [1

Name and define the two main types of chemical reactions that pyruvate undergoes during the link reaction.

• Decarboxylation: The removal of carbon (as a carbon dioxide molecule) [1]

• Dehydrogenation: The removal of hydrogen atoms (protons and electrons) [1]

What happens to the hydrogen atoms removed during the link reaction

• The hydrogen atoms are accepted by the coenzyme NAD (it is reduced) [1]

• The resulting molecule is reduced NAD (do not just write NADH in an OCR exam!) [1]

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What is formed immediately after pyruvate is decarboxylated/dehydrogenated, and what happens to it next?

• A 2-carbon acetyl group (or acetate) is formed [1]

• It combines with Coenzyme A to form Acetyl CoA

State the total net yield of products from the link reaction per molecule of glucose.

• 2 CO2

• 2 reduced NAD

• 2 Acetyl CoA

• (Note: Always check if the exam question says "per pyruvate" or "per glucose"

Explain the function of Coenzyme A once Acetyl CoA has been formed.

• It acts as a carrier molecule to deliver the 2-carbon acetyl group to the Krebs cycle [1]

• It drops it off to combine with 4-carbon oxaloacetate, and then the CoA is recycled