Herbal Medicine18.docx - Degradation of lipids The dietary triacylglycerol phospholipids(PPL and cholesteryl esters are degraded by enzymes from the

Herbal Medicine18.docx - Degradation of lipids The dietary...

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Degradation of lipids The dietary triacylglycerol, phospholipids (PPL) and cholesteryl esters are degraded by enzymes from the pancreas, which is released due to hormonal control. Triacylglycerol molecules are very big so they cannot be taken up effectively by the mucosal cell of the intestinal villi. So that means they have to be dealt with by the enzyme esterase which is a pancreatic lipase, which favours the elimination of FA at carbons one and three. Hydrolysis produces free FA and two-monoacylglycerol which are the main products. The 2nd protein which is colipase, is secreted via the pancreas and binds the lipase at a one to one ratio, this attaches it to the aqueous- lipid interface. If the lipase is inactive, colipase is able to activate it whilst, being surrounded by an inhibitory substance. The majority of cholesterol is in its free form, while ten to fifteen percent of cholestetol is in its esterified form. The pancreatic cholesteryl ester hydrolase hydrolyses cholesteryl esters, which generates cholesterol and free FA’s. Bile salts help to optimise the activity of cholesteryl ester hydrolyse. The juice of the pancreas is abundant in the pro-enzyme of PPL-A2 that, similar to procolipase, needs trypsin to activate it, and similarly to cholesteryl ester hydrolase, need to use bile salts for increased activity. PPL-A2 eliminates one FA from carbon two of PPL, leaving a lysophospholipid. The leftover FA at carbon one can be eliminated by lysophospholipid, which means a glycerylphophoryl base is left, this could result in it being released in the feces to be absorbed. Hydrolytic enzymes that are released via the pancreas degrade lipids in the small intestine which is hormonally controlled. The mucosa cell of the inferior duodenum and jejunum generate tiny peptide hormone, cholecystokinin, in response to be surrounded by lipids and moderately digested proteins which enters these segments of the superior small intestine. Cholecystokinin functions on the gall bladder, and on the exocrine cells of the pancreas. There is also a decline in gastric motility, this leads to a slower secretion of gastric contents into the small intestine. The hormone secretin is produced in other intestinal cell, it is a tiny peptide. When low pH chime enters the intestine the hormone is produce as a response mechanism. The hormone triggers the pancreas and the liver to secrete a solution rich in hydrogen carbonate that aids in the neutralisation of pH intestinal contents, returning them to regular pH levels for digestive activity by pancreatic
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enzymes. Absorption of lipids Free FA, two-monoacylglycerol and free cholesterol are main products of lipid digestion in the jejunum. Additionally, fat soluble vitamins and bile salts; make mixed micelles-disc shaped clusters of amphipathic lipids that coalesce with their hydrophobic and hydrophilic groups.
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