Metab 1 Study Guide 1 Carbohydrates a Monosaccharides i One single molecule of sugar 1 Glucose fructose and galactose b Disaccharides i Combination of two monosaccharides Formed by condensation reactions between two different monosaccharides a Glucose glucose maltose b Glucose fructose sucrose c Glucose galactose lactose c Oligosaccharides i Combination of 3 10 monosaccharides 1 Raffinose 2 Stachyose galactose glucose fructose galactose galactose glucose fructose a Both linked together by 1 4 beta bonds body cannot break these down d Polysaccharides 1 Starch storage form of energy in plants a Amylose alpha 1 4 bonds linear b Amylopectin alpha 1 6 branches and alpha 1 4 straight chains 2 Glycogen storage form of energy in animals a Highly branched chain of glucose molecules e Fiber i Non digestible plant polysaccharides ii Two different types defined by USDA intact in plants 1 Dietary Fiber 2 Functional fiber co2 and short chain fatty acids iii Fiber is fermented by bacteria in the colon producing hydrogen methane gas isolated and extracted added to food f Insoluble vs Soluble fiber i Soluble fiber dissolves in water increases transit time of digestion 1 Ex Pectins gums some hemicelluloses ii Insoluble fiber Does not dissolve in water decreases transit time 1 Increases fecal bulk a Ex Lignans celluloses 2 Digestion of Carbohydrates a Begins in mouth with production of salivary amylase i Breaks down 1 4 bonds not 1 6 bonds b Continues to stomach where different gastric juices are released to further digest food i Stomach is very acidic HCl produced by gastrin inactivates salivary amylase ii Lower esophageal sphincter allows food to enter stomach from esophagus iii Very little carbohydrate digestion occurs in the stomach c Pyloric sphincter of stomach allows chyme to slowly flow into the small intestine Most of the absorption of carbohydrates occurs in the duodenum i Pancreas releases bicarbonate to reduce acidity of chyme ii Digestion and absorption of most carbohydrates occurs inside the villi of the enterocyte The villi contain mini folds called microvilli that absorb monosaccharides 1 Release of lactase sucrase and maltase disaccharides into monosaccharides to break respective 3 Absorption and Transport of Carbohydrates a Absorption occurs through passive facilitated or active transport i Passive diffusion 1 Limited by concentration gradient only small molecules and solutes lipids ii Facilitated diffusion 1 Needs a carrier protein 2 iii Active transport rate of absorption depends on different factors 1 needs a carrier protein requires ATP to pump across concentration gradient a ex sodium potassium pump 4 Carbohydrate Absorption a Glucose and Galactose i Absorption is sodium dependent ii Transported into the cell by SGLT1 1 Sodium required to activate SGLT1 carrier protein iii In order to maintain concentration gradient 3 sodiums pumped out for every 2 potassium in THIS REQUIRES ATP 1 Since absorption of glucose and galactose occur hand in hand with the sodium potassium pump it is considered ACTIVE TRANSPORT iv Transported out of intestine into bloodstream by GLUT2 b Fructose i Facilitated diffusion from carrier protein GLUT5 1 Some fructose can be converted into glucose inside enterocyte ii Transported out of intestine to bloodstream by GLUT2 5 Carbohydrate Transport a Portal Circulation liver i Through facilitated diffusion b Glucose not taken by liver i Facilitated insulin dependent muscle adipose tissue ii Facilitated insulin independent brain kidneys 6 Metabolic Pathways of Carbohydrates a Glycolysis oxidation of glucose for energy production i Occurs in cytosol of muscle and liver cells ii 2 different types 1 Anaerobic without oxygen a Glucose pyruvate lactate 2 Aerobic with oxygen a Glucose pyruvate acetyl CoA STEPS IN GLYCOLYSIS 1 Glucose Glucose 6 Phosphate a Hexokinase glucokinase requires 1 ATP 2 Glucose 6 Phosphate Fructose 6 phosphate a Isomerase 3 Fructose 6 phosphate Fructose 1 6 bisphosphate a Phosphofructokinase requires 1 ATP 4 Fructose 1 6 bisphosphate DHAP OR glyceraldehyde 3 phosphate a Aldolase b DHAP converted to another glyceraldehyde 3 phosphate leaving 2 of g3p Isomerase i 5 Glyceraldehyde 3 phosphate 2 1 3 bisphosphoglycerate 2 a Glyceraldehyde 3 phosphate dehydrogenase yields 2 NADH 6 1 3 bisphosphoglycerate 2 3 phosphoglycerate 2 a Phosphoglycerate kinase yields 2 ATP 7 3 phosphoglycerate 2 2 phosphoglycerate 2 a Phosphoglycerate mutase 8 2 phosphoglycerate 2 phosphenol pyruvate 2 a Enolase 9 Phosphenol pyruvate 2 pyruvate 2 a Pyruvate kinase yields 2 ATP Depending on the type of cellular respiration aerobic anaerobic the last step of glycolysis is different b Anaerobic i Pyruvate Lactate Lactate dehydrogenase requires 2 NADH 1 2 2 ATP total yielded c Aerobic i Pyruvate Acetyl CoA 1 pyruvate dehydrogenase yields 2 NADH 2 acetyl CoA continues to Krebs cycle where energy production is continued 3 yields a total of 14 ATP THE KREBS CYCLE after the Acetyl coA is produced it enters the Krebs cycle for more energy production o CHO fats and proteins can all enter and be oxidized into energy o Occurs in the mitochondrial matrix of muscle and liver cells PRODUCTS o CO2 exhaled by lungs o H2O o Energy GTP 1 ATP NADH 3 ATP FADH 2 ATP NADH and FADH carried onto electron transport chain STEPS OF THE KREBS CYCLE 1 acetyl coA oxaloacetate citrate a citrate 2 citrate cis aconitate intermediate a aconitase 3 cis aconitate isocitrate a Aconitase 4 Isocitrate ketoglutarate a Isocitrate dehydrogenase yields 1 NADH 5 ketoglutarate succinyl CoA a ketoglutarate dehydrogenase yields 1 NADH 6 succinyl CoA succinate a succinyl CoA synthetase yields one GTP 7 succinate fumarate a succinate dehydrogenase yields one FADH 8 fumarate malate a fumarase 9 malate oxaloacetate a malate dehydrogenase yields one NADH After these steps the cycle continues as long as there is sufficient oxaloacetate and acetyl CoA to continue If need be pyruvate can be converted to oxaloacetate at the cost of 1 ATP in order to keep the krebs cycle going A Energy From Krebs cycle a 3 NADH x 3 9 ATP b 1 FADH x 2 2 ATP c 1 GTP 1 ATP i Total 12 ATP produced from krebs cycle directly if beginning from acetyl CoA ii If beginning from pyruvate add 1 more NADH creating 15 ATP d Per one molecule of glucose under aerobic conditions a total of 38 ATP are yielded B Malate Aspartate Shuttle a Moves NADH into mitochondria to the electron transport chain b Kidney liver heart C Glycerol 3 phosphate shuttle a NADH FADH
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