tailieunhanh - Lecture Biochemistry (2/e): Chapter 23 - Reginald Garrett, Charles Grisham

As shown in previous chapter, the metabolism of sugars is an important source of energy for cells. Animals, including humans, typically obtain significant amounts of glucose and other sugars from the breakdown of starch in their diets. Glucose can also be supplied via breakdown of cellular reserves of glycogen (in animals) or starch (in plants). What is the nature of gluconeogenesis, the pathway that synthesizes glucose from noncarbohydrate precursors; how is glycogen synthesized from glucose; and how are electrons from glucose used in biosynthesis? | Chapter 23 Gluconeogenesis. Glycogen Metabolism, and the Pentose Phosphate Pathway to accompany Biochemistry, 2/e by Reginald Garrett and Charles Grisham All rights reserved. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 1 Outline Gluconeogenesis Regulation of Gluconeogenesis Glycogen Catabolism Glycogen Synthesis Control of Glycogen Metabolism The Pentose Phosphate Pathway 2 Gluconeogenesis Synthesis of "new glucose" from common metabolites Humans consume 160 g of glucose per day 75% of that is in the brain Body fluids contain only 20 g of glucose Glycogen stores yield 180-200 g of glucose So the body must be able to make its own glucose 3 Substrates for Gluconeogenesis Pyruvate, lactate, glycerol, amino acids and all TCA intermediates can be utilized Fatty acids cannot! Why? Most fatty acids yield only acetyl-CoA Acetyl-CoA (through TCA cycle) cannot provide for net synthesis of sugars 4 Gluconeogenesis I Occurs mainly in liver and kidneys Not the mere reversal of glycolysis for 2 reasons: Energetics must change to make gluconeogenesis favorable (delta G of glycolysis = -74 kJ/mol Reciprocal regulation must turn one on and the other off - this requires something new! 5 Gluconeogenesis II Something Borrowed, Something New Seven steps of glycolysis are retained: Steps 2 and 4-9 Three steps are replaced: Steps 1, 3, and 10 (the regulated steps!) The new reactions provide for a spontaneous pathway ( G negative in the direction of sugar synthesis), and they provide new mechanisms of regulation 6 Pyruvate Carboxylase Pyruvate is converted to oxaloacetate The reaction requires ATP and bicarbonate as substrates That should make you think of biotin! Biotin is covalently linked to an active site lysine Acetyl-CoA is an allosteric activator The mechanism (Figure ) is typical of biotin! Regulation: when . | Chapter 23 Gluconeogenesis. Glycogen Metabolism, and the Pentose Phosphate Pathway to accompany Biochemistry, 2/e by Reginald Garrett and Charles Grisham All rights reserved. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 1 Outline Gluconeogenesis Regulation of Gluconeogenesis Glycogen Catabolism Glycogen Synthesis Control of Glycogen Metabolism The Pentose Phosphate Pathway 2 Gluconeogenesis Synthesis of "new glucose" from common metabolites Humans consume 160 g of glucose per day 75% of that is in the brain Body fluids contain only 20 g of glucose Glycogen stores yield 180-200 g of glucose So the body must be able to make its own glucose 3 Substrates for Gluconeogenesis Pyruvate, lactate, glycerol, amino acids and all TCA intermediates can be utilized Fatty acids cannot! Why? Most fatty acids yield only acetyl-CoA .

crossorigin="anonymous">
Đã phát hiện trình chặn quảng cáo AdBlock
Trang web này phụ thuộc vào doanh thu từ số lần hiển thị quảng cáo để tồn tại. Vui lòng tắt trình chặn quảng cáo của bạn hoặc tạm dừng tính năng chặn quảng cáo cho trang web này.