Digestion Flashcards
role of protease enzyme
hydrolyse proteins to amino acids
role of lipase enzyme
hydrolyse lipids into glycerol and fatty acids
role of carbohydrase enzyme
hydrolyse carbohydrates to monosaccharides
describe the digestion of starch
- starts in mouth: mastication (chewing), salivary amylase hydrolyses starch to maltose
- in stomach, HCl denatures amylase
- in small intestine: pancreatic amylase continues starch hydrolysis, peristalsis occurs (contraction + relaxation of SI), maltase (membrane-bound enzyme) hydrolyses maltose to glucose
why do soluble disaccharides require hydrolysis
they are too big
name the disaccharides and what membrane-bound enzymes hydrolyse them
- maltose - maltase
- sucrose - sucrase
- lactose - lactase
define digestion
process in which large (insoluble) molecules are hydrolysed by enzymes into small (soluble) molecules, which can be absorbed and assimilated
role of exopeptidase in digestion of proteins
hydrolyse peptide bond of terminal amino acids (ones at the end of the chain)
role of endopeptidase in digestion of proteins
hydrolyse peptide bond of internal amino acids in polypeptide chain
role of dipeptidase in digestion of proteins
hydrolyse peptide bond of single pair of amino acids
benefit of endopeptidase enzyme
produces multiple shorter polypeptide chains, which allows more exopeptidases to hydrolyse more terminal peptide bonds, releasing amino acids faster
describe the mechanism for the absorption of the products of digestion by cells lining the ileum in mammals
- sodium ions are actively pumped out of the cuboidal cells by active, ATP driven Na/K exchange pumps
- sets up a sodium ion concentration gradient with higher concentration of sodium ions on the outside
- co-transporter facilitates the sodium ions to diffuse in down their gradients to ‘pull in’ glucose molecules into the cytoplasm against its gradient (allow for maximum absorption)
- glucose can passively diffuse out through other carrier proteins onto the other side (passing into blood capillaries)
describe the emulsification of lipids
bile salts secreted from liver (act as a detergent) break up globules of triglyceride forming an emulsion. this provides a large surface area for the pancreatic lipase enzyme to hydrolyse the triglycerides into two fatty acids and a monoglyceride (called a micelle)
describe how a micelle enters the smooth endoplasmic reticulum
- micelles are lipid soluble, they diffuse across the cell surface membrane of the cells lining the ileum into the intestinal epithelial cells (carry the fatty acids and monoglycerides)
- form vesicles that merge with the SER
describe what happens to lipids in the SER
micelles formed back into triglyceride molecules
- form chylomicrons ( vesicles of triglycerides surrounded by a phospholipid membrane- contain lipid proteins which determines their role)
- chylomicrons released by exocytosis into the lacteal (can pass into the lymphatic vessels)
