Metab 1 Study Guide1. Carbohydratesa. Monosaccharides i. One single molecule of sugar1. Glucose, fructose, and galactoseb. Disaccharidesi. Combination of two monosaccharides. Formed by condensation reactions between two different monosaccharidesa. Glucose + glucose: maltoseb. Glucose + fructose: sucrose c. Glucose + galactose: lactosec. Oligosaccharides i. Combination of 3-10 monosaccharides1. Raffinose : galactose-glucose-fructose2. Stachyose : galactose- galactose-glucose-fructosea. Both linked together by 1,4 beta bonds, body cannot break these downd. Polysaccharides1. Starch : storage form of energy in plantsa. Amylose, alpha 1-4 bonds, linearb. Amylopectin, alpha 1-6 branches, and alpha 1,4 straight chains2. Glycogen: storage form of energy in animalsa. Highly branched chain of glucose moleculese. Fiberi. Non-digestible plant polysaccharidesii. Two different types defined by USDA1. Dietary Fiber: intact in plants2. Functional fiber: isolated and extracted, added to foodiii. Fiber is fermented by bacteria in the colon, producing hydrogen, methane gas, co2, and short-chain fatty acidsf. Insoluble vs. Soluble fiberi. Soluble fiber: dissolves in water, increases transit time of digestion1. Ex. Pectins, gums, some hemicelluloses ii. Insoluble fiber : Does not dissolve in water, decreases transit time1. Increases fecal bulka. Ex. Lignans, celluloses2. Digestion of Carbohydratesa. Begins in mouth with production of salivary amylasei. Breaks down α1-4 bonds, not α1-6 bondsb. Continues to stomach, where different gastric juices are released to further digest foodi. Stomach is very acidic, HCl produced by gastrin inactivates salivary amylaseii. Lower esophageal sphincter allows food to enter stomach from esophagusiii. 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 duodenumi. Pancreas releases bicarbonate to reduce acidity of chymeii. Digestion and absorption of most carbohydrates occurs inside the villi of the enterocyte. The villi contain mini folds called microvilli, that absorb monosaccharides1. Release of lactase, sucrase, and maltase to break respective disaccharides into monosaccharides. 3. Absorption and Transport of Carbohydratesa. Absorption occurs through passive, facilitated, or active transport i. Passive diffusion1. Limited by concentration gradient, only small molecules and solutes (lipids)ii. Facilitated diffusion1. Needs a carrier protein2. rate of absorption depends on different factorsiii. Active transport1. needs a carrier protein, requires ATP to pump across concentration gradienta. ex) sodium-potassium pump4. Carbohydrate Absorptiona. Glucose and Galactosei. Absorption is sodium dependent! ii. Transported into the cell by SGLT11. Sodium required to activate SGLT1 carrier proteiniii. 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 GLUT2b. Fructosei. Facilitated diffusion from carrier protein GLUT51. Some fructose can be converted into glucose inside enterocyteii. Transported out of intestine to bloodstream by GLUT25. Carbohydrate Transporta. Portal Circulation (liver)i. Through facilitated diffusionb. Glucose not taken by liver i. Facilitated, insulin dependent (muscle, adipose tissue)ii. Facilitated, insulin independent (brain, kidneys)6. Metabolic Pathways of Carbohydratesa. Glycolysis: oxidation of glucose for energy productioni. Occurs in cytosol of muscle and liver cellsii. 2 different types:1. Anaerobic: without oxygena. Glucose → pyruvate → lactate2. Aerobic: with oxygena. Glucose→ pyruvate → acetyl CoASTEPS IN GLYCOLYSIS:1. Glucose →Glucose-6-Phosphatea. Hexokinase/glucokinase, requires 1 ATP2. Glucose-6-Phosphate → Fructose-6-phosphatea. Isomerase3. Fructose-6-phosphate → Fructose-1,6, bisphosphatea. Phosphofructokinase, requires 1 ATP4. Fructose-1,6 bisphosphate → DHAP OR glyceraldehyde-3-phosphate a. Aldolaseb. DHAP converted to another glyceraldehyde- 3-phosphate, leaving 2 of g3pi. Isomerase5. Glyceraldehyde-3-phosphate (2) → 1,3 bisphosphoglycerate (2)a. Glyceraldehyde-3-phosphate dehydrogenase, yields 2 NADH6. 1,3 bisphosphoglycerate(2) → 3 phosphoglycerate (2)a. Phosphoglycerate kinase, yields 2 ATP7. 3 phosphoglycerate(2) → 2 phosphoglycerate (2)a. Phosphoglycerate mutase8. 2 phosphoglycerate (2) → phosphenol pyruvate(2)a. Enolase9. Phosphenol pyruvate(2) →pyruvate (2)a. Pyruvate kinase, yields 2 ATPDepending on the type of cellular respiration (aerobic/anaerobic), the last step of glycolysis is different b. Anaerobici. Pyruvate → Lactate1. Lactate dehydrogenase, requires 2 NADH2. 2 ATP total yieldedc. Aerobici. Pyruvate → Acetyl CoA1. pyruvate dehydrogenase, yields 2 NADH2. acetyl CoA continues to Krebs cycle where energy production is continued 3. yields a total of 14 ATPTHE KREBS CYCLE- after the Acetyl coA is produced, it enters the Krebs cycle for more energy productiono CHO, fats, and proteins can all enter and be oxidized into energyo Occurs in the mitochondrial matrix of muscle and liver cells - PRODUCTS:o CO2 exhaled by lungso H2Oo Energy GTP= 1 ATP NADH= 3 ATP FADH= 2 ATP - NADH and FADH carried onto electron transport chainSTEPS OF THE KREBS CYCLE1. acetyl coA + oxaloacetate → citratea. citrate2. citrate → [cis-aconitate] (intermediate)a. aconitase3. [cis-aconitate] → isocitratea. Aconitase4. Isocitrate → α-ketoglutaratea. Isocitrate dehydrogenase, yields 1 NADH5. α-ketoglutarate → succinyl CoAa. ketoglutarate dehydrogenase, yields 1 NADH6. succinyl CoA → succinatea. succinyl CoA synthetase, yields one GTP7. succinate → fumaratea. succinate dehydrogenase, yields one FADH8. fumarate → malatea. fumarase9. malate → oxaloacetate a. malate dehydrogenase, yields one NADHAfter 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 cyclea. 3 NADH x 3 = 9 ATPb. 1 FADH x 2 = 2 ATPc. 1 GTP = 1 ATPi. Total= 12 ATP produced from krebs cycle directly (if beginning from acetyl
View Full Document
Unlocking...