Carnitine shuttle is involved in -

Ans. is 'b' i.e., Fatty acid oxidation* Very short chain, short chain, medium chain and long chain fatty acids get oxidized in mitochondria* Very short chain, short chain and medium chain fatty acids can cross inner mitochondrial membrane by passive diffusion* Long chain fatty acids cannot cross the inner mitochondrial membrane. Hence they need a carrier. The carrier is carnitine.* Carnitine is b hydroxy g N trimethylaminobutyric acid. It is synthesized from lysine.* In the outer mitochondrial membrane, Carnitine Palmitoyl Transferase I allows carnitine to react with acyl CoA to form Acylcarnitine.* Acyl carnitine crosses the inner mitochondrial membrane with the help of a translocase.* Along the inner mitochondrial membrane, Carnitine Palmitoyl Transferase II acts on acyl carnitine, attaches CoA to it, converting acyl carnitine to acyl CoA. Carnitine, comes out of mitochondria through the same translocase, which transports acyl carnitine inside the matrix.* Now the acyl CoA is ready to get oxidized in the mitochondrial matrix.* Clinical Significance:# Any defect in carnitine shuttle results in defective (3 oxidation of fatty acids. Cardiac muscle fibres, Red muscle fibres are dependent on fatty acid oxidation. Hence it presents with cardiomyopathy and exercise intolerance. Biochemically they present with non ketotic hypoglycemia, hyperammonemia and dicarboxylic aciduria.