Digestive System Lecture Notes PDF

Monday’s office hours will be in ALP 1700 Chemical digestion of protein: endoprotease H2N Ser Pepsin Glu breaks apart Arg protein...

Monday’s office hours will be in ALP 1700 Chemical digestion of protein: endoprotease H2N Ser Pepsin Glu breaks apart Arg protein Phe Tyr Thr Cys Met Ser Val stomach His COOH Chemical digestion of protein: proteases Thr Trypsin (endo) chops middle Cys Met Carboxypeptidases (exo) chops off Ser carboxylend Another class of proteases Val Aminopeptidases H2N His Membrane bound COOH Ser Glu Arg Phe duodenum Tyr startofsmallintestine Absorption of amino acids (AA) 1 AA transported into enterocyte with Na+-dependent AA transporter Intestinal lumen Na+ AA AA transporters “symporter” brings in theamino acids 1 sodiumintotheintestine AA AA transported across 2 2 basolateral membrane by Nd Na+ “antiporter” Nila brings sodium in amino acidsout Na+ a Atpthenbringssodiumout of ATP intestine kt intointestine K+ Na+ Blood Digestive system II Lecture 19 Digestive system Lecture 19A Learning goals Chemical digestion for carbohydrates and lipids HCL formation Motility  NADH NADH Pyruvate 2 2 34 Chemical digestion of carbohydrate/starch CH2OH CH2OH CH2OH CH2OH CH2OH H O O O O O H H H H H H OH H OH H OH H OH H OH H OH O O O O OH H OH H OH H OH H OH H OH Amylase Challenge=the bonds chops largecarbs Amylase cuts every 3-7 alpha 1-4 bonds. CH2OH CH2OH H O O H Disaccharide (maltose) H OH H H OH H OH O OH H OH H OH Maltase cutsbtwn 2 glucosemol CH2OH H O H Monosaccharide (glucose) H OH H Absorbable OH OH 1 glucosemolecule H OH Absorption of monosaccharides Sodium Glucose Transporter glucose fructose K SGLT GLUT5 giviose natGLUT2 GLUT2 i Absorption of monosaccharides There is still more sodium outside than inside V goes Tith DIFY.EE a kt needed Absorption of monosaccharides Key Intestinal lumen SGLT GLUT2 CH2OH CH2OH O H GLUT5 H O H OH H OH H CH2OH OH H Na+ OH OH OH H H OH CH2OH O CH2OH H H O H H OH OH H OH H CH2OH Na+ OH OH H OH OH H ATP K+ Blood Chemical digestion of lipids is complex enzyme lipasecuts Ester bonds Glycerol-3 carbon chain Triglyceride rich hydrogen Chemical digestion of lipids is complex Lipase from the pancreas hydrolyzes 2 fatty acids from triacylglycerides Challenge-Ester bond is protected  Bile salts from the gallbladder break up micelles goal release thefattyacids for absorption Challenge=expose the ester bonds to be attacked by lipase Lipid digestion and absorption is complex 1 1 Bile salts coat and emulsify micelles Lipid digestion and absorption is complex 1 Bile salts coat and emulsify micelles 2 Lipase generates fatty acids that 2 collect at middle of small micelles Lipid digestion and absorption is complex 1 Bile salts coat and emulsify micelles 2 Lipase generates fatty acids that collect at middle of small micelles 3 3 Free fatty acids diffuse across Lipid digestion and absorption is complex 1 Bile salts coat and emulsify micelles 2 Lipase generates fatty acids that collect at middle of small micelles 4 3 Free fatty acids diffuse across 4 Cholesterol by facilitated diffusion Lipid digestion and absorption is complex 1 Bile salts coat and emulsify micelles 2 Lipase generates fatty acids 3 Free fatty acids diffuse across 4 Cholesterol by facilitated diffusion 5 5 Triacylglycerides re-formed. These and cholesterol combine with proteins to form chylomicrons Craig end Lipid digestion and absorption is complex 1 Bile salts coat and emulsify micelles 2 Lipase generates fatty acids that collect at middle of small micelles 3 Free fatty acids diffuse across 4 Cholesterol by facilitated diffusion 5 Triagylglycerides re-formed. These and cholesterol combine with proteins to form chylomicrons 6 6 Chylomicrons exit via exocytosis, enter lymph system, then blood Secretion of H+ in the stomach is complex Stomach 1 Lumen Water dissociates H+ moved out by HKA H2O 1 2 H+ H+ + OH- ATP HKA CA makes HCO" ! Carbonic 2 anhydrase HCl K+ 3 K+ HCO" ! Bystem HCO"! CO2 exchanged for Cl- 4 leathannel 3 Cl- Cl- Cl- 4 Cl- exits through Parietal Cell channel, HCl formed by accumulating H+ and Cl- Contractions keep digesta moving Duodenum 12 waves/min Stomach 3 waves/min Generated by Interstitial Cells of Cajal (ICC)- pacemakers Three patterns of contraction 1) Peristalsis moves food unidirectionally (tube of toothpaste) 2) Migrating motor complex - empty gut at night 3) Segmental contractions cause mixing Segmental contractions cause mixing T0 T1 Predominant in the large intestine goodbacteria liningtheintestine moves things around inthe stomach