This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
Long chain fatty acids penetrate the inner mitochondrial membrane as? 
Select and explain. 
A. Carnitine derivatives, B. Pyruvate, C. Acetyl coA derivatives, D. Acyl CoA
A: Carnitine derivatives
Answer: A: Carnitine derivatives 
Explanation: Long-Chain Fatty Acids Penetrate the Inner Mitochondrial Membrane as Carnitine Derivatives
Carnitine ( -hydroxy- -trimethylammonium butyrate), (CH3)3N+—CH2—CH(OH)—CH2—COO–, is widely distributed and is particularly abundant in muscle. Long-chain acyl-CoA (or FFA) cannot penetrate the inner membrane of mitochondria. In the presence of carnitine, however, carnitine palmitoyltransferase-I, located in the outer mitochondrial membrane, converts long-chain acyl-CoA to acylcarnitine, which is able to penetrate the inner membrane and gain access to the -oxidation system of enzymes. Carnitine-acylcarnitine translocase acts as an inner membrane exchange transporter. Acylcarnitine is transported in, coupled with the transport out of one molecule of carnitine. The acylcarnitine then reacts with CoA, catalyzed by carnitine palmitoyltransferase-II, located on the inside of the inner membrane, reforming acyl-CoA in the mitochondrial matrix, and carnitine is liberated.