02082011SPRNTR342-CarbMetabolism1

02082011SPRNTR342-CarbMetabolism1 - Carbohydrate Metabolism...

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1 Carbohydrate Metabolism 1 Reading: Gropper, 4 th ed, Ch 4, pp. 79–87; Ch 3, pp. 57–62 Gropper, 5 th ed, Ch 3, pp. 71–82; Ch 1, pp. 20–26
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2 Objectives for today: Review glucose absorption into tissues and maintenance of blood glucose levels Overview of glucose metabolism Glycogenesis and glycogenolysis
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3 Overview Once taken into the cell, glucose will either be: Stored (as glycogen) But most glycogen is made from gluconeogenic precursors rather than dietary glucose Used for energy production (ATP) Stored as fat (fatty acids) Used to make amino acids or DNA/RNA
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4 Table 3-1, p. 66
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5 Glucose absorption Glucose (and galactose) are absorbed by active transport into the enterocyte via the s odium- gl ucose t ransporter 1 (SGLT1) requires ATP carrier must be preloaded with Na + gene mutations associated with glucose- galactose malabsorption [GLUT5 transports fructose and some glucose; see next lecture ]
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6 Active transport Energy (ATP) Cell membrane Fig. 2-21c, p. 48
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7 Microvillus Na + -driven glucose symport Transport protein mediating facilitated diffusion of glucose Lumen of gut Intestinal epithelium Na + /K + ATPase Blood ATP ADP + P Glucose Na + Na + Na + K + Fig. 1-17, p. 16 Glucose Glucose SGLT1
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8 Glucose transport Glucose leaves the enterocyte by 3 routes: 15% leaks back into the intestinal lumen 25% diffuses through the basolateral membrane (back side) into the circulation ~60% is transported into circulation via facilitated diffusion using a specific carrier (GLUT2) (a small portion is used by the cell)
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9 Glucose transport Glucose is transported by a family of glucose transporters (GLUT) Transport is by facilitated diffusion All cells express at least one GLUT isoform GLUT 2 transports glucose from within the small intestinal enterocyte to the bloodstream
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This note was uploaded on 05/10/2011 for the course NTR 342 taught by Professor Tillman during the Spring '09 term at University of Texas at Austin.

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02082011SPRNTR342-CarbMetabolism1 - Carbohydrate Metabolism...

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