BIOLOGY 151 1st Edition Lecture 32 Outline of Last Lecture 1. Digestion2. Oral cavity3. Stomach4. How do things get across membranes?Outline of Current Lecture 1. GI tract2. Regions of GI tract3. Small intestine4. Fluid handling by GI tract5. CTFRCurrent Lecture - 4/10GI tract:- different enzymes with different pH optima regions with different absorptive properties- acid - solubilizes food, denatures proteins, antibacterial, activates pepsinogen- positive feedback- acid neutralized by pancreatic juice- pumps - ATP- transports - cotransporters and antiporters- glucose carried with sodium gradient (high to low conc.)- antitransporter example bicarbonate goes down gradient, brings chloride into cell- channels - gated- voltage, ligands- carbonic anyhydrase- H+/K+ pump- HCO3-/Cl- antiporter- Cl- channel- K+ channel- all three use energy, just different formsRegions of GI tract:- oral cavity, pharynx, esophagus, stomach, lumen of small intestine- epithelium of small intestine- carbohydrate, protein, nucleic acid, lipid digestionSmall intestine:- lumen- villi and microvilli increase surface area for absorption and water handlingThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- control of water secretion in small intestine- Na+/K+/2Cl- cotransporter- regulated Cl- channel- aquaporin- most of hydrolysis for food and most of absorption of nutrients- intestinal enzymes that hydrolyze proteins, carbohydrates, nucleic acids, and lipids are made in pancreas inform of zymogens (inactive precursors) that are secreted from granules by exocytosis then activated in the lumen of the intestine, similar to pepsin- pancreas secrets bicarbonate to neutralize stomach acid - digestion of fats is helped by bile salts like cholic acid - steroid that makes an emulsion of the fats and lets lipase go to work- bile salts made in liver, stored in gallbladder, and delivered to small intestine along with pancreatic juicesFluid handling by GI tract: - normally large intestine removes almost all the fluid that enters - cholera epidemics- bacteria that cause diarrhea produce toxins that change the control of water secretion in small intestine- secretion of water into intestinal lumen is unregulated and increases beyond capacity of large intestine to reabsorb waterCFTR:- Cystic Fibrosis Transmembrane-Conductance Regulator- channel only open if phosphorylated - protein kinase gets activated to stick the terminal phosphate from ATP onto the channel = causes the channel to open- hormones normally activate kinase- mucus in lungs- bacterial toxins in diarrhea bind to receptors on luminal surface and lead to increase in concentration of 2nd messengers, activating kinase, opening channel, water secretion into intestinal lumen- treatment is water and salt
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