Where does the link reaction (pyruvate decarboxylation) occur in eukaryotic cells?

• A. In the cytoplasm
• B. In the mitochondrial matrix
• C. On the inner mitochondrial membrane
• D. In the nucleus

Answer: (B)

Verified step by step guidance

1. Understand the context: The link reaction, also known as pyruvate decarboxylation, is a critical step in cellular respiration where pyruvate is converted into acetyl-CoA. This process links glycolysis to the citric acid cycle (Krebs cycle).
2. Recall the location of glycolysis: Glycolysis occurs in the cytoplasm, producing pyruvate. The pyruvate must then be transported into the mitochondria for further processing.
3. Identify the site of the link reaction: Pyruvate is transported into the mitochondrial matrix, where the enzyme pyruvate dehydrogenase catalyzes its decarboxylation, producing acetyl-CoA, NADH, and CO₂.
4. Eliminate incorrect options: The cytoplasm is where glycolysis occurs, not the link reaction. The inner mitochondrial membrane is involved in the electron transport chain, not pyruvate decarboxylation. The nucleus is unrelated to this process.
5. Conclude that the correct answer is the mitochondrial matrix, as this is where the link reaction takes place in eukaryotic cells.