Lipid Catabolism

Contents of this page:
Fatty acids & triacylglycerols
Fatty acid activation & transport
Fatty acid b-Oxidation
Ketone bodies

A 16-carbon fatty acid, with numbering conventions, is shown at right. Most naturally occurring fatty acids have an even number of carbon atoms. The pathway for catabolism of fatty acids is referred to as the b-Oxidation Pathway, because oxidation occurs at the b-carbon (C3).

Triacylglycerols (triglycerides) are the most abundant dietary lipids. They are the form in which we store reduced carbon for energy. Each triacylglycerol has a glycerol backbone to which are esterified 3 fatty acids. Most triacylglycerols are "mixed." The three fatty acids differ in chain length and number of double bonds Lipid digestion, absorption and transport will be covered separately.
Lipases hydrolyze triacylglycerols, releasing one fatty acid at a time, producing diacylglycerols, and eventually glycerol.

Glycerol arising from hydrolysis of triacylglycerols is converted to the Glycolysis intermediate dihydroxyacetone phosphate, by reactions catalyzed by:
(1) Glycerol Kinase
(2) Glycerol Phosphate Dehydrogenase.

Free fatty acids, which in solution have detergent properties, are transported in the blood bound to albumin, a serum protein produced by the liver.
Several proteins have been identified that facilitate transport of long chain fatty acids into cells, including the plasma membrane protein CD36.

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