hydrolyzes triacylglycerol into two free fatty acids and 2-monoacylglycerol. The enzyme is attached to the luminal surface of capillary endothelial cells via a highly charged membrane-bound chain of heparin sulfate-proteoglycans. The ability of lipoprotein lipase to bind both the chylomicron particle and the cell surface ensures the cellular uptake of free fatty acids that are generated from the hydrolysis. Once inside the cell, free fatty acids can be oxidized to provide energy, metabolized to biologically active compounds, incorporated into phospholipid and cholesteryl ester, or resynthesized into triacylglycerol for storage as a potential reservoir of fatty acids for subsequent use.
triacylglycerol, and these make up the bulk of the fat both in the human diet and in the body. The melting point of a triacylglycerol is determined by the position of the fatty acids esterified to glycerol and physical characteristics—their chain length and number, position, and conformation of the double bonds, and the stereochemical position.
Approximately 90% of the molecular weight of triacylglycerol is accounted for by the fatty acids. The fatty acid profile of the diet is reflected, in part, in the fatty acid profile of the adipose tissue triacyl-glycerol. Such data have been used to approximate long-term food intake patterns of humans. Manipulating the dietary fat provided to domesticated animals is being considered as one approach to modifying the fatty acid profile of meat.
Mono- and diacylglycerols have one and two fatty acids, respectively, esterified to glycerol. They rarely occur in large quantities in nature. Mono- and dia-cylglycerols are primarily intermediate products of triacylglycerol digestion and absorption, clearance from the bloodstream, or intracellular metabolism. They are frequently added to processed foods because of their ability to act as emulsifiers. Their presence in food products is noted on ingredient labels.
Once consumed, triacylglycerol are hydrolyzed to free fatty acids and monoglycerides in the small intestine prior to absorption. These compounds enter the intestinal cell and are used to resynthesize triacylglycerol. This lipid is then incorporated into a nascent triacylglycerol-rich lipoprotein particle, termed chylomicron, for subsequent release into peripheral circulation. Chylomicrons are secreted directly into the lymph prior to entering the bloodstream. Once in circulation, triacylglycerol are hydrolyzed before crossing the plasma membrane of peripheral cells for subsequent metabolism. The primary enzyme that hydrolyzes triacylglycerol in plasma is lipoprotein lipase. Lipoprotein lipase
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