How are fatty acids activated?

Fatty acids are activated to form fatty acyl CoA molecules via a two-step process. This happens when the fatty acids enter the cytosol and react with coenzyme A (CoA). Fatty acid activation occurs in the endoplasmic reticulum and requires ATP (adenosine triphosphate). 

• In the first step, adenine monophosphate from ATP is transferred to the fatty acid, forming acyl-AMP. The pyrophosphate that is released during this reaction gets hydrolyzed into two orthophosphates, which drives the activation reaction to the next step.  
• In the second step, the reaction between the acyl-AMP and a coenzyme A molecule results in the formation of fatty acyl-CoA, and the AMP is released. The activated fatty acid is transported into the matrix of the mitochondria.