biol 66 lab 13

4 layers of stomach

1) mucosa 2) submucosa 3) muscularis 4) serosa

why doesn't the stomach normally digest itself??

- secretion of mucus from gastric glands - mucus protects the lining of the stomach from the acidic contents of the stomach lumen

describe the structural adaptations of the small intestine that help increase the rate at which the products of digestion can be absorbed

- plicae = folds in the walls of the digestive tract - villi = folds in the epithelium - microvilli = folds in the cell membrane of intestinal cells - ALL INCREASE SURFACE AREA

portal triad

hepatic portal vein, hepatic artery, bile duct

describe several functions of the liver & its anatomical connection to the alimentary canal (GI tract)

- production of bile - storage of fat (triglycerides) - storage of carbs (glycogen) - conjugation of toxins to water-soluble molecules - bile stored in gallbladder & delivered to small intestine for emulsification of fat

describe the sources of digestive enzymes along the alimentary canal

- salivary glands = amylase, lipase - gastric gland(s) = pepsin - intestinal epithelium = brush border enzymes - pancreas = pancreatic enzymes

compare the effects of hydrochloric acid (HCl) on protein digestion by pepsin vs the effects of HCl on starch digestion by salivary amylase

- low pH environment is essential to the function of pepsin ; prevents the function of salivary amylase

how does fat digestion affect the pH of fluids in the lumen of the alimentary canal??

- results in formation of fatty acids & therefore lowers the pH of the lumen of the alimentary canal

carbohydrate digestion ~ starch + ???

tube: distilled water tube: amylase tube: amylase + HCl tube: boiled amylase

which tube in the carbohydrate digestion had the most complete digestion & why?

tube w/ starch + amylase b/c the correct enzyme was present

why were the other tubes in the carbohydrate digestion exp. "wrong"?

tube with distilled water = no enzyme present tube with amylase & HCl = wrong pH (too acidic) tube with boiled amylase = denatured enzyme

which tubes in the carbohydrate digestion exp. had the presence of starch after adding Lugol's solution?

- starch + distilled water - starch + amylase + HCl - starch + boiled amylase

protein digestion ~ protein (egg white) + ... ?

tube: pepsin + distilled water tube: pepsin + HCl @ 37 deg. celsius tube: pepsin + HCl @ 0 deg. celsius tube: HCl + water tube: pepsin + NaOH

which tube in the protein digestion exp. had the most complete digestion & why?

tube with protein + pepsin + HCl @ 37 deg. celsius b/c correct enzyme was present, correct temperature, correct pH (pepsin prefers acidic pH since our stomach is acidic)

why were the other tubes in the protein digestion exp. "wrong"?

tube with pepsin = wrong pH tube with pepsin & HCl @ 0 deg. celsius = wrong temperature tube with HCl & water = no enzyme present tube with pepsin & NaOH = wrong pH (NaOH too basic)

appearance of each tube in the protein digestion exp (in terms of digestion)?

tube with protein & pepsin = slightly less tube with protein + pepsin + HCl @ 37 deg. celsius = a LOT less tube with protein + pepsin + HCl @ 0 deg. celsius = same tube with protein + HCl = same tube with protein + pepsin + NaOH = same-ish

fat digestion: ~ cream + ... ?

tube: bile salts tube: pancreatic lipase tube: bile salts + pancreatic lipase tube: distilled water

which tube in the fat digestion exp. had the most complete digestion & why?

tube with bile salts & pancreatic lipase b/c bile salts act as emulsifier & enzyme is present

why were the other tubes in the fat digestion exp. "wrong"?

tube with bile salts = no enzyme present tube with pancreatic lipase = enzyme present ; no emulsifier present tube with distilled water = nothing in here

pH changes in the fat digestion exp?

cream + bile salts = no change cream + pancreatic lipase = decrease pH cream + bile salts + pancreatic lipase = LARGE pH change cream + distilled water = no change