Beta-oxidation
In biochemistry and metabolism, beta-oxidation is the catabolic process by which fatty acid molecules are broken down in the cytosol in prokaryotes and in the in eukaryotes to generate acetyl-CoA, which enters the citric acid cycle, and NADH and FADH2, which are co-enzymes used in the electron transport chain. It is named as such because the beta carbon of the fatty acid undergoes oxidation to a carbonyl group. Beta-oxidation is primarily facilitated by the , an enzyme complex associated with the , although some fatty acids are oxidized in peroxisomes.
Fatty acid catabolism consists of:
Free fatty acids cannot penetrate any biological membrane due to their negative charge. Free fatty acids must cross the cell membrane through specific transport proteins, such as the SLC27 family fatty acid transport protein. Once in the cytosol, the following processes bring fatty acids into the mitochondrial matrix so that beta-oxidation can take place.
Once the fatty acid is inside the , beta-oxidation occurs by cleaving two carbons every cycle to form acetyl-CoA. The process consists of 4 steps.
Fatty acids are oxidized by most of the tissues in the body. However, some tissues such as the red blood cells (which do not contain mitochondria), and cells of the central nervous system (because fatty acids cannot cross the blood-brain barrier into the interstitial fluids that bathe these cells) do not use fatty acids for their energy requirements, but instead use carbohydrates or ketone bodies.
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