Which molecule is involved in the transport of fatty acids in cells?

• A. ATP
• B. Carnitine
• C. Glucose
• D. Cholesterol

Answer: (B)

Carnitine plays a crucial role in the transport of fatty acids into the mitochondria, where they are oxidized for energy production. Fatty acids are usually too large to cross the mitochondrial membrane freely, so they are first converted into acyl-CoA derivatives. However, these acyl-CoA molecules cannot pass through the mitochondrial membrane directly.

Carnitine facilitates this process by forming a complex with acyl groups, transforming acyl-CoA into acylcarnitine. This acylcarnitine can then shuttle across the mitochondrial membrane through specialized transport proteins. Once inside the mitochondria, the acyl group is released, allowing it to re-form acyl-CoA and enter the beta-oxidation pathway, ultimately leading to ATP production.

The other molecules mentioned do not serve this specific function. ATP is primarily involved in energy transfer, glucose is a key energy source but does not transport fatty acids, and cholesterol is crucial in membrane structure and steroid hormone synthesis, not in fatty acid transport. Thus, carnitine is essential for enabling fatty acid metabolism within the mitochondria.