In a typical eukaryotic cell, where does the Krebs (citric acid) cycle primarily occur?

• A. In the nucleus
• B. In the cytosol
• C. On the inner mitochondrial membrane (cristae)
• D. In the mitochondrial matrix

Answer: (D)

Verified step by step guidance

1. Recall that the Krebs cycle, also known as the citric acid cycle, is a key metabolic pathway involved in cellular respiration.
2. Understand that cellular respiration occurs in different parts of the cell, with glycolysis happening in the cytosol and the electron transport chain on the inner mitochondrial membrane.
3. Identify that the Krebs cycle takes place in the mitochondrial matrix, which is the fluid-filled space inside the inner membrane of mitochondria.
4. Note that the mitochondrial matrix contains the enzymes necessary for the Krebs cycle to convert acetyl-CoA into carbon dioxide and high-energy electron carriers.
5. Conclude that among the given options, the correct location for the Krebs cycle is the mitochondrial matrix.