Which molecule is required to transport long-chain fatty acids into mitochondria for beta-oxidation?

Which molecule is required to transport long-chain fatty acids into mitochondria for beta-oxidation?

• A. Carnitine
• B. NAD+
• C. FAD
• D. CoA

Answer: (A)

Long-chain fatty acids can’t cross the inner mitochondrial membrane on their own, so they rely on the carnitine shuttle to enter the matrix for beta-oxidation. In the cytosol, the fatty acid is first activated to fatty acyl-CoA. Then CPT I transfers the acyl group to carnitine, forming acylcarnitine, which is shuttled across the inner membrane. Inside the matrix, CPT II transfers the acyl group back to CoA to reform fatty acyl-CoA for beta-oxidation. Thus, carnitine is the molecule that enables transport into the mitochondria. The other components play roles in the oxidation steps themselves or in initial activation, not in the transport across the mitochondrial membranes.

Long-chain fatty acids can’t cross the inner mitochondrial membrane on their own, so they rely on the carnitine shuttle to enter the matrix for beta-oxidation. In the cytosol, the fatty acid is first activated to fatty acyl-CoA. Then CPT I transfers the acyl group to carnitine, forming acylcarnitine, which is shuttled across the inner membrane. Inside the matrix, CPT II transfers the acyl group back to CoA to reform fatty acyl-CoA for beta-oxidation. Thus, carnitine is the molecule that enables transport into the mitochondria. The other components play roles in the oxidation steps themselves or in initial activation, not in the transport across the mitochondrial membranes.