Fatty acid oxidation is dependent on entry of fatty acids into the mitochondria, which provides substrate for beta-oxidation in the mitochondrial matrix. The fatty acids are transported in as acylcarnitines.
Step 1 in beta-oxidation happens when a fatty acyl CoA that's made at the inner surface of the inner mitochondrial membraine is oxidized by acyl-CoA dehydrogenase. The flavoprotein enzyme uses FAD to accept an electron to complete the reaction. The products end up being trans-enoyl CoA and FADH2, which transfers electrons into the oxidative phosphorylation pathway to recreate FAD.
Step 2 in beta-oxidation is hydration of trans-enoyl CoA producing 3-L-hydroxyacyl CoA.
Step 3 is when 3-L-hydroxyacyl CoA is oxidized to 3-ketoacyl-CoA intermediate and generates NADH.
Step 4 occurs when beta-ketoacyl-CoA thiolase cleaves the 3-ketoacyl-CoA to produce a 2-carbon atom short fatty acyl-CoA and acetylCoA.
Acetyl CoA is then ready to enter in the TCA cycle for ATP energy production, and FADH2 and NADH will also be reoxidzed in the ETS to produce ATP energy.