Lecture 34-35

Lecture 34-35 - Lecture 34-35 Glycolysis Glucose 1 Major...

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Lecture 34-35: Glycolysis Glucose 1. Major pathways of carbohydrate metabolism either begin or end with glucose 2. Major form of absorbed carbohydrate 3. The only fuel used to any significant extent by a few specialized cells, and the major fuel used in brain 4. Metabolism is defective in 2 very common metabolic disease: obesity and diabetes a. They’re risk factors for atherosclerosis, hypertension, small vessel disease, kidney disease, and blindness 5. Disaccharides that serve as important sources of glucose in our diet a. 6. most of the glucose passes through the cells of the intestinal tract into the portal vein blood and then the general circulation to be used by other tissues Overview 1. Glycolysis a. Pathway used by all cells of the body to extract part of the chemical energy inherent in the glucose molecule in the form of ATP b. converts glucose to pyruvate and sets the stage for complete oxidation of glucose to CO2 and H2O 2. Gluconeogenesis a. glucose synthesis in liver and kidneys b. uses same enzymes from the glycolytic pathway, although the reactions catalyzed are in the opposite direction c. requires ATP only some of the enzyme catalyzed steps can be common to both the glycolytic and gluconeogenic pathways 3. Glycogensis : glycogen synthesis for glucose storage 4. Glycogenolysis : Glycogen degredation Glycolysis 1. Anaerobic fermentation 2. Produces 2 ATP from 1 glucose w/o O2 3. Critical at birth to conserve O2 for the brain 4. Pyruvate can be completely oxidized to CO2 and H2O by enzymes housed in mitochondria a. Glycolysis therefore sets the stage for aerobic oxidation of carbohydrate b. The overall process of Glycolysis plus the subsequent mitochondrial oxidation of pyruvate to CO2 and H2O has the following equation 5. Brain – absolute need for glucose and O2 120 g/day for ATP 6. RBCs – lack mitochondria anaerobic metabolism to lactate 7. Kidney medulla, testis, leukocytes, white muscle fibers have few mitochondria and synthesize ATP anaerobically (40g/day) Glycogen 1. storage form of glucose 2. converted to glucose or glucose-6-phosphate 3. Liver is a primary source
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4. Liver actively removes glucose from portal vein 5. Liver dumps glucose into circulation when plasma levels fall (glycogenolysis or gluconeogeneis) 6. Liver is first to sense glucagon and insulin from the pancreas Red Blood Cells 1. GLUT-1 2. No mitochondria 3. pentose phosphate pathway generates NADPH Brain 1. GLUT-3 (insulin independent) 2. Pentose phosphate pathway generates NADPH Muscle + Heart 1. GLUT-4 (insulin dependent) 2. Pentose phosphate pathway generates NADPH Adipose 1. GLUT-4 (insulin dependent) 2. Pentose phosphate pathway generates NADPH for FA synthesis Liver 1. GLUT-2 (insulin independent) a. Low affinity (skims) b. High capacity 2. Pentose phosphate pathway generates NADPH + ribose phosphate (DNA + RNA) Glucoruonic Acid Pathway 1. Gluconeogenesis: glucose from lactate, pyrucvate, glycerol, serine glycine, alanine
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Lecture 34-35 - Lecture 34-35 Glycolysis Glucose 1 Major...

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