Pancreatic juice is rich in the proenzymes of phospholipase A2, which is converted to active form with the help of trypsin. Phospholipase A2 converts the fatty acid at carbon 2 of the phospholipids, leaving a lysophospholipid. For example, lecithin is converted to lysolecithin. The remaining fatty acid at carbon 1 is cleaved by lysophospholipase, producing glycerylphosphorylcholine…
Cholesteryl esters are hydrolysed by cholesteryl hydrolase, resulting in cholesterol and free fatty acids.
Triacylglycerols are too large to be taken by the mucosal cells of the intestinal villi. Hence, they are acted upon by an esterase, pancreatic lipase, which removes the fatty acids at carbon 1 and 3. The resulting products of hydrolysis are a mixture of 2-monoacylglycerol and free fatty acids. A second protein, colipase is secreted by…
The hydrolytic enzymes that degrade the dietary lipids in the intestine are secreted by the pancreatic juice in the pancreas. The secretion of this enzyme is under the control of hormones. A small peptide hormone cholecystokinin, also known as pancreozymin, is produced by the cells in the mucosa of jejunum and lower duodenum. This hormone…
In duodenum, the critical process of emulsification of the dietary lipids occurs. Because these compounds are practically insoluble in water, the enzymic hydrolysis of lipids of triacylglycerol can occur only on the surface of a lipid droplet, which is at the interface between the lipid droplet and the surrounding aqueous solution. Figure 10.1 Overview of Lipid…
The digestion of lipids starts in the stomach, catalysed by an acid-stable lipase, which originates in the glands at the back of the tongue, known as lingual lipase. However, the rate of hydrolysis is very slow because the lipid is not emulsified for the digestion process. Lipase can hydrolyse or degrade triacylglycerol only in the…
The intake of an adult is about 60–150 g of lipids per day, of which 90% is usually triacylglycerol. The remaining dietary lipids are cholesterol, cholesteryl esters, phospholipids, and unesterified (free) fatty acids.
SECTION A