Digestion and absorption Flashcards
Explain the digestion of carbohydrates?
Amylase catalyses the hydrolysis reaction that hydrolyses the alternate glycosidic bonds in starch to produce the disaccharide maltose. The acidic pH of the stomach denatures the amylase and prevents further hydrolysis of the starch, so when the food passes into the small intestines it mixes with pancreatic juice that contains amylase to continue the breakdown of starch to maltose. The pancreas and intestinal walls produce alkaline salts to keep a neutral pH to allow the amylase to function. Maltase is produced by the epithelial cells lining the small intestines, it hydrolyses the maltose to alpha glucose.
Explain the emulsification of lipids before they can be digested?
In the stomach, solid lipids are turned into a fatty liquid consisting of large fat droplets. When they arrive at the small intestines, bile salts made by the liver and stored in the gallbladder is secreted. The bile salts break down the large fatty droplets into smaller ones. Emulsification increases the surface area of the fatty droplets for action by lipases.
Explain the digestion of lipids by lipases?
Takes place in the lumen of the small intestines. The lipases are produced and secreted by the pancreas into the small intestines, where they catalyse the breakdown of lipids into monoglycerides and fatty acids.
Explain how proteins are digested by endopeptidases and exopeptidases?
Endopeptidases hydrolyse the peptide bonds within proteins to create smaller polypeptide chains.
Exopeptidases hydrolyse the terminal peptide bonds to remove individual amino acids.
Dipeptidases are exopeptidases that work on dipeptides. They hydrolyse the peptide bonds in dipeptides to produce amino acids. Dipeptidases are located in the cell surface membrane of epithelial cells in the small intestines.
