<Li> Once inside the cell long - chain - fatty - acid--CoA ligase catalyzes the reaction between a fatty acid molecule with ATP (which is broken down to AMP and inorganic pyrophosphate) to give a fatty acyl - adenylate, which then reacts with free coenzyme A to give a fatty acyl - CoA molecule . </Li> <Li> In order for the acyl - CoA to enter the mitochondrion the carnitine shuttle is used: </Li> <Ol> <Li> Acyl - CoA is transferred to the hydroxyl group of carnitine by carnitine palmitoyltransferase I, located on the cytosolic faces of the outer and inner mitochondrial membranes . </Li> <Li> Acyl - carnitine is shuttled inside by a carnitine - acylcarnitine translocase, as a carnitine is shuttled outside . </Li> <Li> Acyl - carnitine is converted back to acyl - CoA by carnitine palmitoyltransferase II, located on the interior face of the inner mitochondrial membrane . The liberated carnitine is shuttled back to the cytosol, as an acyl - CoA is shuttled into the matrix . </Li> </Ol> <Li> Acyl - CoA is transferred to the hydroxyl group of carnitine by carnitine palmitoyltransferase I, located on the cytosolic faces of the outer and inner mitochondrial membranes . </Li>

Relevance of activation of fatty acid in lipid metabolism