Final answer:
Fatty acyl-carnitine is the molecule that can cross the inner mitochondrial membrane facilitated by the carnitine transport system, which includes enzymes like carnitine acyltransferase I and II, as well as the carnitine-acylcarnitine translocase transport protein.
Step-by-step explanation:
The inner mitochondrial membrane is a selective barrier that is impermeable to many molecules, including most forms of acyl-CoA. In the context of fatty acid metabolism, the transport of fatty acids across the inner mitochondrial membrane is facilitated by the conversion of fatty acyl-CoA to fatty acyl-carnitine. This is possible through a two-step reaction involving the enzymes carnitine acyltransferase I and II, also known as CPTI and CPTII respectively. These reactions entail the initial formation of fatty acyl-carnitine at the outer mitochondrial membrane, followed by its facilitated diffusion into the mitochondrial matrix. Once inside, fatty acyl-carnitine is converted back into fatty acyl-CoA by carnitine acyltransferase II. To answer the student's question, option B) Fatty acyl-carnitine is the molecule that can cross the inner mitochondrial membrane.