Question

Explain how fatty acids are activated in the cytoplasm and ultimately transported into the mitochondrion to be oxidized. Why would the use of carnitine be an advantage for this process?

Answer 1

Fatty acids are activated in the cytoplasm by acyl-CoA synthetase, requiring ATP. Carnitine then helps transport the activated fatty acids into the mitochondria by forming a fatty acyl-carnitine complex. This provides an efficient pathway for the fatty acids to be oxidized into acetyl-CoA for ATP production.

Step-by-step explanation:

The process by which fatty acids are activated in the cytoplasm involves their conversion into fatty acyl Coenzyme A (fatty acyl CoA) through the catalytic action of acyl-CoA synthetase. This reaction consumes one ATP molecule and produces AMP. The activated fatty acids, in the form of fatty acyl CoA, cannot directly penetrate the mitochondrial membrane due to its impermeability to acylated fatty acids. Herein lies the role of carnitine.

Carnitine facilitates the transport of activated fatty acids into the mitochondria by forming a fatty acyl-carnitine complex in the presence of the enzyme carnitine acyl transferase-I. This complex then crosses the inner mitochondrial membrane via a transport protein known as carnitine acyl carnitine translocase. Once inside the mitochondrial matrix, carnitine acyl transferase-II converts the fatty acyl-carnitine back into fatty acyl-CoA and releases carnitine for reuse.