biol 66 lab 13

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4 layers of stomach

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GI system -- overview & application questions

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4 layers of stomach

  1. mucosa

  2. submucosa

  3. muscularis

  4. serosa

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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

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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

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portal triad

hepatic portal vein, hepatic artery, bile duct

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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

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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

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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

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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

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carbohydrate digestion

~ starch + ???

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

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

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

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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

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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

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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

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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)

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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)

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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

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fat digestion:

~ cream + ... ?

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

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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

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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

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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

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