Physiology Week 7 Lecture 13
Physiology Week 7 Lecture 13 IPHY 3470
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This 2 page Class Notes was uploaded by Sydney Lazzell on Thursday October 6, 2016. The Class Notes belongs to IPHY 3470 at University of Colorado at Boulder taught by Christopher DeSouza in Fall 2016. Since its upload, it has received 7 views. For similar materials see Human Physiology 1 in integrated physiology at University of Colorado at Boulder.
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Date Created: 10/06/16
IPHY 3470: Human Physiology 1 Week 4 Lecture 8 Membrane Transporters • Gated channels or open channels o Can’t be open on both sides • Different kinds of carriers: 1. Uniport = 1 molecule, flow in one direction only (in or out) 2. Symport = 2 molecules can move in but only one direction 3. Antiport = opposite direction, 1 coming in and one going out Diffusion • Passive • High to low concentration • Rapid • Directly related to molecular size • Inversely related to molecular size • Open system or across a partition • Net movement until concentration is equal Simple diffusion • Fick’s Law • Facilitated diffusion o Brings glucose into cell, down concentration gradient (uniport) o Diffusion reaches equilibrium when concentrations in/out of cell are equal § High [glu]out [glu]in stays low GLUT Family • GLUT 1: glu & hexoses – most tissues of body (cell membrane) o Facilitated diffusion • GLUT 2: glu & hexoses – liver, intestine, kidney • GLUT 3: glu & hexoses - neurons • GLUT 4: glu only – skeletal muscle (regulated by insulin) o Muscle & adipose tissue • GLUT 5: fructose – intestinal epithelium • Insulin stimulates GLUT 4 = greater glucose disposal Glucose Transport into Cell • Uptake into muscle/cells occur via glu transporters • Transporters: o Non-insulin (GLUT 1) o Insulin mediated (GLUT 4) • Resting muscle most of glu enters GLUT 1 transporters residing permanently in plasma membrane • Exercise stimulated glu uptake is also through GLUT 4’s o Majority stored in intracellular vesicles & are trans -located to plasma membrane when stimulated Insulin Mediated Glucose Uptake (GLUT 4) • Bind to specific insulin receptor on muscle cell surface = exocytosis of GLUT 4 rich intracellular vesicles causing a 10-fold increase in the # of plasma membrane transporters • All transporters activated together = net result is that glu uptake increases 10-20x • Contraction has similar “insulin like” effect of glu uptake into muscle • Loss/removal of insulin = deactivated transporters • Ability of contraction to cause increase in glu transporters is important where working muscle cells can uptake glu even when insulin levels fall during exercise o Ex: day 6 of food strike = muslces are sucking in glu & your body has to stay laying down b/c too weak Exercise & Glucose Transport • Glu transport is rate limiting step in glu utilization under physiological insulin concentration (glu --> into the cell) • Acute exercise: single bout of exercise o Increase GLUT 4 trans-location o Increase # of plasma o Membrane GLUT 4 protein o Ex: diabetics GLUT 4 After Exercise • No additive effect on levels of GLUT 4 between insulin, exercise, and both exercise & insulin • GLUT 4 levels much higher in trained men than in sedentary o Can increase GLUT 4 with training
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