Question

Which one of the following statements about fatty acids is true?

A) When fatty acids are activated in the cytosol, ATP is converted to ADP

B) Fatty acyl groups are covalently linked to carnitine by an enzyme inhibited by malonyl CoA

C) Fatty acids are very soluble in water and need no carrier in the blood

D) Fatty acids are linked to glycerol phosphate in the fasting state

E) Fatty acids can be oxidized to CO2 and H2O in the mitochondria of red blood cells

Answer 1

Fatty acids are activated before they undergo beta oxidation in the mitohondria.The fatty acids have to be transported from the cytosol to the mitochondrial matrix for beta oxidation to take place. The first step in fatty acid activation is conversion of fatty acids to acyl CoA by forming thioester linkage between the fatty acid and coenzyme A. In the next step Carnitine acyltransferases form bonds between fatty acyl coA to carnitine to facilitate transport of fatty acids across the membrane.

However Carnitine acyl transferase enzyme is inhibited by malonyl coA if fatty acid synthesis needs to take place. Malonyl coA prevents beta oxidation of fattya cids by inhibiting carnitine acyl transferase during fatty acid synthesis.

Hence Statement B -Fatty acyl groups are covalently linked to carnitine by an enzyme inhibited by malonyl CoA is true about fatty acids.