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CORNELL NS 3310 - Describes Insulin Effects and Introduction to Pathways of Metabolism

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NS 3310 1st Edition Lecture 8Outline of Past LectureI. Review of Cholesterol Gallstone Disease: FXRII. Absorption of Glucose, Galactose, and FructoseIII. Glucose TransportersIV. Glycemic Response to CarbohydrateOutline of Current LectureI. InsulinII. Integrated MetabolismCurrent LectureI. Insulin- Very powerful anabolic hormone- Role in cellular glucose absorption and metabolism-Binds to membrane insulin receptor-Stimulates GLUT4 exocytosis to move to membrane in adipocytes and myocytes -Promotes glucose phosphorylation and anabolism - Required for maintenance of blood glucose levels 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.- It is the only hormone that can reduce our blood glucose level while glucagon helps to raise blood glucose level- Glucagon counteracts effects of insulin; it stimulates the breakdown of glycogen. It does this by binding to a G-protein receptor on surface, activating the receptor and producing cAMP from adenylate cyclase from ATP. cAMP then activates protein kinase which has multiple targets it can phosphorylate to regulate glycogen breakdown- Insulin reacts with a membrane receptor that uses a second messenger to carry out its action. Insulin is a potent anabolic hormone promoting the storage of carbs, lipids, and proteins. It does so by increasing the expression of activity of enzymes that catalyze the synthesis of glycogen, lipids and protein - Once insulin is released, there is a large accumulation of GLUT4 at surface; if insulin low, GLUT4 accumulates in storage in center II. Integrated Metabolism- After glucose gets into the cell, it enters glycolysis and can be turned into a fatty acid, enter pentose phosphate pathway, be stored as glycogen - When glucose comes from extracellular space, it goes into cell through glucose transporter. It is then phosphorylated by kinases. In liver it is phosphorylated by glucose kinase and in muscle hexokinase 1 and 2. Purpose of phosphorylation is to trap glucose into cell, raise energy levels and reduce the free glucose level in the cell. Without the phosphorylation, we would have high concentration of glucose in cells- The end product of glycolysis is 2 pyruvate and 2 ATP-Under anaerobic conditions, pyruvate is converted to lactate which is then cycled back to liver- Pyruvate goes to the mitochondria and is converted to acetyl-coA in the citric acid cycle (TCA cycle) in order to generate ATP and NADH-Citrate is an important regulator of energy metabolism. If there is a lot of citrate, it tells the body that there is sufficient energy. Citrate can go back to cytosol and convert to acetyl-coA and make fatty acid-Gluatamine can convert to citrate- The activity of certain metabolic pathways is regulated according to the energy needs in such a way that some may be stimulated and others may be suppressed- Glycogenesis is the conversion of glucose to glycogen- Glycogenolysis is the breakdown of glycogen to glucose and regulation of


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