Promotes glycogenolysis and gluconeogenesis o

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Unformatted text preview: d taken up by cells of the body (used or stored) Sugar Transport by GLUT Transporters • GLUT 1 o glucose uptake in red blood cells and the brain • GLUT 2 o glucose, fructose, galactose uptake in the liver (two way transporter) • GLUT 3 o glucose uptake in the brain • GLUT 4 o insulin- mediated glucose uptake by muscles and adipose tissue The Pancreas, Insulin and Glucagon • islets of Langerhans – endocrine cells in pancreas • beta cells secrete insulin • alpha cells secrete glucagon • delta cells secrete somatostatin What does insulin do? • mediates transport of glucose from the blood stream into cells (muscle cells, fat cells) • inhibits glycogenolysis and gluconeogenesis o glycogenolysis - breakdown of glycogen to produce glucose o gluconeogenesis – breakdown of stored fat and protein to make glucose • promotes energy storage (glycogen and fat production) and building of body tissues (proteins) o considered anabolic What does glucagon do? • promotes glycogenolysis and gluconeogenesis o considered catabolic • inhibits energy storage (glycogen and fat production) and building of body tissues Fed State • high blood sugar promotes insulin release from the pancreas o insulin stimulates formation of glycogen (glucose converted to glycogen in the liver) lowered blood sugar o insulin stimulates glucose uptake from the blood into tissue cells (muscle, kidney, fat) lowered blood sugar Fasted State • low blood sugar promotes glucagon release from the pancreas glucagon stimulates the breakdown of glycogen in the liver glycogen converted to glucose glucose released into blood raises blood sugar Insulin and the Regulation of Glucose Transporters • glucose transporters stored within cell in membrane vesicles • when insulin interacts with its receptor, vesicles move to surface and fuse with the plasma membrane, increasing the number of glucose transporters in the PM • when insulin levels drop, glucose transporters are removed from the PM by endocytosis, forming small vesicles • smaller vesicles fuse with larger endosome • patches of endosome enriched for glucose transporters bud off to become small vesicles, ready to return to the surface when insulin levels rise again Glucose Transport • not all glucose transport is insulin dependant o brain, blood cells, liver use transporters that are NOT insulin dependant • other hormones influence glucose metabolism o epinephrine – increases glucose uptake into muscles not insulin dependant happens in stress, during exercise o epinephrine, cortisol, and growth hormone promote glycogenolysis and gluconeogenesis promote an increase in blood glucose levels Abnormal Insulin and/or Glucagon • hyperglycemia o prediabetes, diabetes • hypoglycemia Hypoglycemia • low blood glucose - blood glucose drops to an abnormal amount • two types: 0. Fasting • tumours, liver disease, alcoholism, endocrinopathies o pancreatic tumour: too many beta cells result in too much insulin o liver: might not be able to release glucose or break down glycogen • diabetic hypoglycemia – too much insulin or oral diabetes meds 1. Reactive / Post- Prandial • may be early (2- 3 hours after eating) or late (3- 5 hours after) • dumping syndrome: if part of intestine is removed, food can hit intestine too quickly blood glucose levels skyrocket huge spike in insulin release huge drop in blood glucose levels Hypoglycemia Symptoms • Epinephrine- Like o faintness, weakness, tremors, heart palpitations, sweating, hunger, nervousness these symptoms indicate that glycogen mobili...
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