Final answer:
Carnitine is required to transport activated long-chain fatty acids into the mitochondria for β-oxidation. It helps convert fatty acids to a form that can cross the mitochondrial membrane to undergo further oxidation.
Step-by-step explanation:
The correct answer to the question is a. carnitine. The process of transporting activated long-chain fatty acids into the mitochondria for β-oxidation is a two-step process involving carnitine. Firstly, in the cytosol, fatty acids are converted into fatty acyl CoA. This fatty acyl CoA is then combined with carnitine, creating a fatty acyl carnitine molecule, which is the form that can be transported across the mitochondrial membrane. Once inside the mitochondria, the molecule is converted back into fatty acyl CoA. From there, the fatty acid can undergo further oxidation in the mitochondrial matrix to produce acetyl CoA, which then enters the Krebs cycle to participate in energy production.