In order to transport long-chain fatty acids from the cytosol to the mitochondria, three of the following molecules are required. Which one is NOT necessary?

Question

In order to transport long-chain fatty acids from the cytosol to the mitochondria, three of the following molecules are required.  Which one is NOT necessary?

Quizplus · Accepted Answer

11ecba2d_0e7b_c64c_a3bf_27afc2a5c0d0_MD0008_00 Entry into the mitochondrial matrix is tightly regulated by the inner mitochondrial membrane. Crossing the membrane generally requires the aid of transport proteins, which only recognize specific molecules. Some short-chain fatty acids can cross the inner mitochondrial membrane directly, but long-chain fatty acids can only cross the outer mitochondrial membrane. Additionally, long-chain fatty acids are not recognized by any transport proteins; they must be modified or "activated" to enter the matrix. Fatty acid activation and transport includes the following steps: In the cytosol, the enzyme acyl-CoA synthetase catalyzes the reaction of fatty acids with coenzyme A to form acyl-CoA molecules. This reaction is thermodynamically unfavorable and requires ATP hydrolysis to proceed (Choices A and B). Acyl-CoA molecules then migrate to the intermembrane space, where they can react with carnitine to form acylcarnitine. The transport protein acylcarnitine translocase, located on the inner mitochondrial membrane, recognizes acylcarnitine and carries it into the mitochondrial matrix (Choice C). Acylcarnitine is then converted back to acyl-CoA and carnitine. Acyl-CoA is subsequently digested by β-oxidation, and carnitine is transported out of the matrix where it can pick up and carry a new fatty acid into the mitochondrial matrix. Although oxaloacetate is an intermediate in the citric acid cycle, gluconeogenesis, and transport of acetyl-CoA from the mitochondria into the cytosol for fatty acid synthesis, it is not involved in transport of fatty acids from the cytosol into the mitochondria. Educational objective: Entry into the mitochondrial matrix is tightly regulated by transport proteins in the inner mitochondrial membrane. Fatty acids must be activated with coenzyme A followed by carnitine to enter the mitochondrial matrix. Activation requires ATP hydrolysis.

In Order to Transport Long-Chain Fatty Acids from the Cytosol