* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download complete
Survey
Document related concepts
Biosynthesis wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Metabolomics wikipedia , lookup
Oxidative phosphorylation wikipedia , lookup
Microbial metabolism wikipedia , lookup
Lactate dehydrogenase wikipedia , lookup
Fatty acid metabolism wikipedia , lookup
Amino acid synthesis wikipedia , lookup
Pharmacometabolomics wikipedia , lookup
NADH:ubiquinone oxidoreductase (H+-translocating) wikipedia , lookup
Basal metabolic rate wikipedia , lookup
Blood sugar level wikipedia , lookup
Citric acid cycle wikipedia , lookup
Metabolic network modelling wikipedia , lookup
Nicotinamide adenine dinucleotide wikipedia , lookup
Transcript
Chapter 4 Carbohydrates Objectives: • Learn the major sources of dietary carbohydrates. – What are these digested to and absorbed as? – What are the major types of glucose transporters and where are they found? How are these transporters regulated? • Understand how the major carbohydrates are utilized metabolically by your cells – Understand the basic processes involved in glycolysis, glycogenesis, glycogenolysis, gluconeogenesis, and the hexosemonophosphate shunt – Understand how fructose and galactose enter these pathways • Learn how these pathways are regulated by insulin and glucagon – What are the major ways that regulation takes place (mechanisms of regulation)? • Learn how ethanol consumption impacts the metabolic pathways for carbohydrates – – – – • Acetaldehyde toxicity High NADH:NAD+ ratio Substrate competition Induced metabolic tolerance Learn how some diseases are associated with carbohydrate metabolism – Diabetes – Hypoglycemia Enzymes involved in carbohydrate digestion and metabolism are stereospecific for D sugars Reference molecule Chiral carbon? Anomeric carbon? Fig. 4-2, p. 74 Pentoses? Reducing sugars? Oligosaccharides? Table 4-1, p. 75 Fig. 4-5a, p. 77 Fig. 4-6, p. 78 Table 4-2, p. 81 Golgi Apparatus Glucose Transport Vesicle-bound transporters Translocation Synthesized transporters from ribosomes Insulin Insulin receptor Fig. 4-8, p. 82 (a) Glucose (reference food) (b) Low glycemic index (c) Fasting baseline Hours Glucose meal Fig. 4-9, p. 83 Cereals Snacks Pasta Beans All Bran 51 chocolate bar 49 fettucini 32 baked 44 Bran Buds + psyll 45 corn chips 72 linguini 50 black beans, boiled 30 Bran Flakes 74 croissant 67 macaroni 46 butter, boiled 33 Cheerios 74 doughnut 76 spagh, 5 min boiled 33 cannellini beans 31 Corn Chex 83 graham crakers 74 spagh, 15 min boiled 44 garbanzo, boiled 34 Cream of Wheat 66 jelly beans 80 Soups/Vegetables kidney, boiled 29 Frosted Flakes 55 pizza, cheese & tom 60 carrots, fresh, boil 49 kidney, canned 52 Grapenuts 67 Pizza Hut, supreme 33 corn, sweet 56 lentils, green, brown 30 muesli, natural 54 popcorn, light micro 55 parsnips 97 lima, boiled 32 potato chips 56 peas, fresh, boil 48 navy beans 38 pinto, boiled 39 Fruit apple 38 Power bars 58 Drinks apricots 57 pretzels 83 apple juice 40 red lentils, boiled 27 banana 56 saltine crakers 74 colas 65 soy, boiled 16 cantalope 65 Cereal Grains Gatorade 78 Breads cherries 22 barley 25 orange juice 46 bagel, plain 72 dates 103 basmati white rice 58 Milk Products baquette, Frnch 95 grapefruit 25 bulgar 48 ice cream, van 60 pita 57 grapes 46 couscous 65 ice milk, van 50 pizza, cheese 60 kiwi 52 skim milk 32 Fig. 4-10, p. 84 Fig. 4-11a, p. 85 Glycogen synthase – active when dephosphorylated, inactive when phosphorylated; insulin vs. glucagon Fig. 4-11b, p. 85 Glycogenolysis – activated by glucagon and epinephrine through action on glycogen phosphorylase (phosphorylase a, phosphorylated – active; phosphorylase b, dephosphorylated - inactive Fig. 4-12, p. 86 Fig. 4-13, p. 87 Fig. 4-14, p. 88 1. Citrate synthase 2. Aconitase 3. Isocitrate dehydrogenase 4. a ketoglutarate dehydrogenase 5. Succinyl thiokinase 6. Succinate dehydrogenase 7. Fumarase 8. Malate dehydrogenase Fig. 4-15, p. 91 Fig. 4-16, p. 91 Fig. 4-17, p. 93 Used when nucleic acids are needed Used when NADPH is needed Fig. 4-19, p. 95 Brain, neurons, and RBCs are dependent on glucose as a nutrient. When dietary intake of glucose is decreased and glycogen stores are depleted, we can make new glucose from alternative fuel sources in a process called gluconeogenesis Fuels used to make new glucose include • amino acids, • lactate, • Glycerol Organ which most often performs gluconeogenesis is the liver Irreversible rxn Fig. 4-21, p. 97 Four Mechanisms for Regulating Blood Glucose • Allosteric modulation by compounds within the pathways • Hormonal activation of covalent modification of specific enzymes • Directional shifts in reversible reactions by changes in reactant or product concentrations • Translocation of enzymes within the cell • Citrate synthase • Aconitase • Isocitrate dehydrogenase a ketoglutarate dehydrogenase • Succinyl thiokinase • Succinate dehydrogenase • Fumarase • Malate dehydrogenase Regulated by NADH/NAD+ Regulated by ATP/ADP Fig. 4-15, p. 91 Fig. 4-22, p. 101 Ethyl Alcohol: Metabolic Impact • Ethyl alcohol most closely resembles a carbohydrate • It has caloric value, and is a common dietary component of alcoholic beverages • Each gram of alcohol yields 7kcal of energy – May account for 10% of total energy intake in moderate consumers – May account for 50% of total energy intake in alcoholics. • Ethanol is absorbed throughout the digestive tract and is transported in the blood. • It is then oxidatively degraded, mostly in the liver, to acetaldehyde and then to acetate. Acetate eventually is converted to acetylcoA – Alcohol dehydrogenase – MEOS or cytochrome P-450 – catalase ethanol + NAD+ ----> acetaldehyde + NADH Acetaldehyde is toxic reactive with amino groups and may interact with proteins competes for the plasma carrier of pyridoxal (vitamin B6) acetaldehyde + NAD+ ----> acetic acid + NADH Acetic acid can lead to acidosis Because the two reactions require NAD+, NADH can build up. What problems might this cause? anaerobic metabolism to regenerate NAD+ lack of pyruvate for gluconeogenesis - hypoglycemia Fig. 4-23, p. 102 Metabolic consequences • • • • Acetaldehyde toxicity Elevated NADH:NAD+ ratio Metabolic competition Induced metabolic tolerance • Elevates HDL in serum and lowers serum lipoproteins • Slowing development of smooth muscles in atherosclerosis Diseases of Carbohydrate Metabolism • Diabetes • Hypoglycemia