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DIGESTION SUMMARY MOUTH Salivary gland Starch –Amylase maltose STOMACH Hydrochloric acid Gastric juices – controlled by hormone called Gastrin – food in mouth Pepsinogen –contact with acid Pepsin Proteins –pepsin polypeptides Mucin – forms a layer of mucus After 3-4 hours - chyme DUODENUM Pancreas o Starch –amylase Maltose o Lipids –Lipase Fatty acids and glycerol o Trypsinogen –activated by enterkinase made in intestinal glands Trypsin (endopeptidase) o Chymotrypsinogen – trypsin activates Chymotrypsin (exopeptidase) o Proteins –(Trypsin + Chymotrypsin) polypeptides + amino acids Liver o Bile Emulsify fats micelles o Sodium hydrogen carbonate - Neutralises acidic chime SMALL INTESTINE Wall of Small Intestine o Pancreozymin (CCK) – is produced when fat-rich chime enters the duodenum. Triggers release of pancreatic enzyme and release of Bile. o Secretin – triggered from acidic chime - stimulates flow of hydrogen carbonate ions from pancreas o Enterkinase – activates trypsinogen trypsin o Starch –amylase maltase o Maltase –maltose glucose o Sucrose –sucrase glucose and fructose o Lactose –lactase glucose and glactose o Dpeptides –peptidase amino acids o Peptides –aminopeptidase amino acids o Nucleotides—neucleotidase organic base + pentose sugar + phosphate Absorption o Epithelium secretes sodium and chloride ions into the lumen water potential gradient water moves into lumen by osmosis o Absorption of glucose Sodium is responsible for the absorption of water, amino acids and glucose Glucose is absorbed by active transport – requires sodium dependent glucose transporters – proteins transport both sodium and glucose into the cell Once inside the epithelium, glucose and sodium must be exported from the cell into the blood – diffusion Other monosaccharides such as fructose are not absorbed by active transport o Absorption of amino acids Sodium-dependent amino acid transporters Active transport of sodium and amino acids o Absorption of Lipids o Emulsification bile salts and lipids micelles o Fatty acids and monoglycerides are absorbed by simple diffusion across plasma membrane LARGE INTESTINE Water and electrolytes (i.e. sodium and chloride) are absorbed Na+ transported from lumen by sodium pumps, water follows by osmosis Bicarbonate is secreted to neutralise acids generated from microbes