Bio Lab 16: Digestive System2022/2023

Purpose of lab -examine anatomy of digestive system of fetal pig & learn how some enzymes of human digestive system fxn 3 enzymes analyzed 1) amylase 2) pepsin 3) lipase Starch -polysaccharide composed of glucose units in long branching chains Where does digestion of starch begin? With what enzyme? -mouth w/ enzyme salivary amylase Where does digestion of starch continue? With what enzyme? -duodenum through activity w/ enzyme pancreatic amylase Hydrolysis of starch -releases maltose (disaccharide) What is used to monitor the activity of the enzyme amylase on starch? -iodine test Control samples in iodine test -positive=two drops starch -negative=two drops dH2O -add I2KI to both -blue/black=POSITIVE result for starch -yellow=NEGATIVE result for starch Results of enzymatic breakdown of starch by salivary amylase -once amylase added, blue/black turned into yellow -amylase breaking down starch Protein breakdown by pepsin -begins in stomach -continues in duodenum Proteins -macromolecules constructed of 1+ polypeptide chains Peptides -chains of 50- AA Biuret reagent -detects presence/absence of protein 1) absence of protein = blue 2) presence of protein = purple 3) presence of peptides = pink Results of protein breakdown -PINK b/c proteins broken down into peptides Lipid digestion -begins in duodenum w/ secretions of bile from liver & lipase from pancreas -bile salts emulsify fats so tiny lipid droplets can more easily react w/ enzyme lipase -end products=fatty acids & glycerol How will we investigate how bile & lipase work? -w/ the pH indicator PHENOL RED Why is NaOH added initially -make soln alkaline so we can see change as pH lowers Phenol red color ranges -acidic: yellow -neutral: peach -basic: pink Lipid digestion results -w/ bile salts & lipase = clearish yellow/peach -w/ just lipase = opaque tan/peach Layers of tissue comprising small intestine -mucosa -submucosa -muscularis (longitudinal & circular) -serosa Villi -fingerlike extensions projecting inward toward lumen -comprise the mucosa -outer layer of columnar epithelial cells Microvilli (brush border) -on exposed surface of columnar epi cells of villi -further enhance surface area & absorptive capabilities of intestine Goblet cells -secrete mucus Lacteal -blood vessels & a lymphatic vessel -within center of each villus