HNF 461 1st Edition Lecture 14 Outline of Last Lecture I Categorization of Fiber a Dietary b Functional c Solubility II Fiber in Grains III Soluble Fiber a Physiological Effects b Fermentation IV Insoluble Fiber a Constipation V Oligosaccharides Outline of Current Lecture I Glucose Uptake General Information II Glucose Transporters a GLUT 1 5 b Km Levels III Monosaccharide Absorption a Glucose Galactose b Fructose IV Regulation of Glucose Transport V Monosaccharide Transport Uptake a Role of Insulin VI Fate of Glucose Current Lecture Glucose Uptake These 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 1 Glucose Uptake General Information a Glucose is a polar molecule so cannot diffuse across cell membrane alone b Needs a protein carrier 2 Glucose Transporters a GLUT 1 4 i GLUT1 and 3 basal uptake in many tissues ii GLUT2 liver pancreatic beta cells enterocytes and selected brain cells iii GLUT3 brain iv GLUT4 muscle and adipose tissue regulated by insulin b Km Levels The value of substrate that is needed in order to reach half of maximum enzyme activity i GLUT1 very low Km ii GLUT2 high Km iii GLUT3 very low Km iv GLUT4 Intermediate physiological Km 3 Monosaccharide Absorption a Glucose Galactose two ways to enter enterocytes i Na dependent transporter requires ATP ii GLUT2 transporter no energy required iii At low glucose concentrations Na dependent transporter transports more glucose into cells than GLUT2 iv At higher glucose concentrations GLUT2 transports more glucose into cells that Na dependent transporter b Fructose i GLUT5 transporter into enterocytes 4 Regulation of Glucose Transport a Amount of GLUT2 on the cell surface is controlled by glucose levels more glucose more GLUT2 b Sugar in the blood leads for the hormone GIP GLP 1 to release insulin triggers the absorption of glucose i When insulin is released it also will inhibit the function of GLUT2 to inhibit glucose absorption in the small intestine c GIP slows down the release of food from the stomach to the small intestine 5 Monosaccharide Transport Uptake a When monosaccharides are absorbed into the small intestine then travels to the liver where fructose galactose some glucose are removed b Role of Insulin i Increased blood glucose increase in insulin secretion ii Insulin binds to insulin receptors on cell membranes This triggers the translocation of GLUT4 from the particles vesicles in the cells to the cell membranes increase in glucose uptake by cells iii Insulin inhibits the intake of glucose in the small intestine 6 Fate of Glucose a Provides Fuel for ATP synthesis i In the brain red blood cells skeletal muscle b Glycogenesis c Synthesis of ribose NADPH and glucose for glycoprotein glycolipid synthesis d Lowest priority fatty acid and TAG synthesis
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