HUN3224 Oral cavity Esophagus Exam 1 CHO and GI Tract o Enzymes and lysozymes present in saliva o Bolus food and saliva mixture o No digestion o Epiglottis blocks airways when swallowing o Lower esophageal sphincter relaxes to let food into the stomach constricts to keep food from moving back into esophagus GERD gastroesophageal reflux relaxation of lower esophageal sphincter Heartburn caused when stomach acid and food return to esophagus Over time can damage esophagus leading to esophageal ulcer and Possible causes spicy foods caffeine pregnancy fatty foods increased risk of esophageal cancer Stomach o Holds food Doesn t really absorb or digest Mechanical mixing and breakdown o Gastric secretions Gastrin stimulates release of HCl and pepsinogen HCl kills bacteria denatures proteins converts pepsinogen to pepsin inactivates lingual lipase Pepsinogen inactive precursor to pepsin Mucus protects stomach lining contains bicarbonate Neutralizes acid coming in contact with stomach lining Intrinsic factor necessary for absorption of B12 Pyloric Sphincter Small intestine o Separates stomach from duodenum o Sections duodenum jejunum ileum Duodenum main site of digestion and absorption o Receives secretions from other digestive organs i e pancreas gallbladder o Lining in small intestine Folded into finger like projections called villi Villi covered with microvilli o Forms the brush border o Microvilli is part of the enterocytes cells that line villi Digestion of nutrients primarily completed on brush border Enterocytes Tip cells slough off every few days to renew cells HUN3224 Mid villar cells will move to top secrete digestive enzymes Most everything is digested by this point Crypt cells cell replication Take nutrients in but also produce enzymes for macronutrient absorption o Smooth lining no villi has colonocytes instead o Water and electrolyte absorption Large intestine Accessory organs o Pancreas Acini secrete enzymes into GI tract Zymogens inactive enzymes Islet tissue secrete hormones into blood insulin glucagon somatostatin o Liver Makes bile Emulsifier for fat digestion made from cholesterol Stored in gallbladder After digestion of fats bile is reabsorbed in ileum and dent back to liver Metabolizes drugs alcohol and other toxins Transport proteins Albumin Circulation of nutrients Approximately of total caloric intake comes from carbohydrates Simple glyceraldehyde v complex glycogen Monosaccharides o Glucose Hexose Most abundant o Fructose o Galactose Hexose Hexose o Ribose Disaccharides Pentose o Formed from 2 monosaccharides Maltose Sucrose Glucose glucose HUN3224 Lactose Glucose fructose Glucose galactose Sucrose v high fructose corn syrup o Sucrose solid form 50 glucose 50 fructose o HFCS liquid form 45 glucose 55 fructose Oligosaccharides o 3 10 monosaccharides Polysaccharides o Starch Raffinose Stachyose Galactose glucose fructose Galactose galactose glucose fructose Storage form of CHO in plants Amylose o Linked by 1 4 bonds o Digested readily linear molecule o 15 20 starch content Amylopectin o Branched chain made up of 1 4 long chains and 1 6 branches o 80 85 starch content o Glycogen o Fiber Highly branched similar to amylopectin in structure Made in liver and muscle Dietary found in plants Functional extracted manufactured Soluble decreases transit time moves things through gut faster Insoluble increases transit time Insoluble does not mean indigestible Fermented by bacteria in colon o Short chain fatty acids function to Stimulate water and sodium absorption into mucosa Provide colonocytes with energy Enhance immune function Reduce atrophy of gut Gaps between colonocytes o Cause bacteria and excess content to filter into bloodstream HUN3224 causing sepsis Decrease pH of gut Inhibits cholesterol synthesis in liver Digestion of CHO begins in the mouth o Salivary amylase Only digests 1 4 bonds HCl in the stomach inactivates salivary amylase Pancreas secretes bicarbonate to neutralize acid chyme from the stomach Brush border enzymes made by enterocytes o Sucrose o Lactase o Maltase o Break disaccharides down into their monosaccharide components Absorption and transport of CHO occurs via facilitated diffusion and active transport o Facilitated diffusion carrier protein assists in the movement of the membrane o Rate of diffusion determined by Concentration gradient Amount of carrier available Rapidity of solute carrier protein Rapidity of conformation change of carrier o Active transport similar but also requires ATP Because the system is pumping against the concentration gradient o Glucose enters enterocytes attached to sodium SGLT1 In order to prevent Na from being too high inside the membrane Na K pump is used to pump Na out This goes against the concentration gradient Therefore ATP needed for Na K pump This process also occurs for galactose o Glucose transporter SGLT1 Travels through enterocytes capillaries portal system liver o Fructose absorbed via facilitated diffusion GLUT5 transporter This does not require a sodium transport o GLUT2 movement across basolateral membrane of enterocytes fructose transport at liver Takes everything to liver to be metabolized o GLUT4 insulin stimulated uptake of glucose at muscle heart adipocytes o GLUT5 absorption of fructose at small intestine o SGLT1 uptake of glucose and galactose from lumen Liver Portal Circulation o Liver prefers to use fructose and galactose other tissues prefer glucose o At typical intakes little to no fructose or galactose in in peripheral blood Metabolic pathways of CHO HUN3224 o Glycolysis Location cytosol Types Anaerobic o Without oxygen Glucose pyruvate lactate Energy production 2 ATP 0 NADH Aerobic o With oxygen Glucose pyruvate acetyl CoA Energy production 2 ATP 2 NADH After formation of pyruvate pyruvate enters mitochondria for Krebs NADH enters ETC Glucokinase Hexokinase Functions in liver and pancreas Upregulated by insulin Functions in muscle adipose brain Down regulated by glucose 6 phosphate o Krebs Cycle Amphibolic pathway CHO fats and proteins can all enter and be completely oxidized into CO2 H2O and energy 1NADH 3ATP 1FADH 2ATP 1GTP 1ATP Glycolysis Krebs Total Energy molecule ATP NADH FADH GTP 2 2 0 0 0 8 2 2 2 10 2 2 ATP 2 30 4 2 38 Energy production from 1 molecule of glucose under aerobic conditions o Shuttle Systems Malate Aspartate Shuttle Moves NADH into mitochondria ETC Active in kidney liver heart o Full 38 ATP can form to remember Malate Aspartate Shuttle MAS more in Spanish because more
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