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Metabolism of Nutrients II HUN3226 Exam 1 Study Guide THE GI TRACT Stomach Small intestine Lining Holds food Mechanical mixing and breaking down of food Gastric secretions Absorption of alcohol and asprin Secretion of intrinsic factor o Folded into fingerlike projections called villi which are lined with enterocytes o Villi are covered with microvilli o Microvilli brushborder o Digestion of nutrients usually completed on brush border Duodenum Transport mechanisms across the cell membrane Jejunum digestion and absorption continures Ileum absorption enterohepatic circulation of bile o Passive diffusion does not require energy driven by growth of entropy of the sys o Facilitated diffusion spontaneous passive transport of molecules or ions across a membrane via specific transmembrane integral proteins o Active transport movement against a concentration gradient uses energy o Endocytosis energy using process by which cells take in molecules by engulfing Large Intestine Smooth lining no villi Water and electrolyte absorption Intestinal microflora o Bacterial breakdown of fiber o Produce vitamin K and biotin Temporary storage and concentration until defecation Liver Main site for vitamin storage Converts vitamins to metabolically active form Metabolizes drugs alcohol and other toxins METABOLISM OF VITAMINS AND MINERALS Vitamins Organic contain carbon Essential cannot be made by the body o Exceptions niacin vitamins K and D Not energy yielding provides no kcal Vulnerable to destruction sunlight heating cooking processing Water soluble absorbed in portal blood and excreted in urine o B1 thiamin o B2 riboflavin o B3 Niacin o B5 pantothenic acid o B6 pyridoxine o B7 biotin o B9 folate o B12 cobalamin o Vitamin C living organisms Macro vs Microminerals o Macrominerals o Microminerals Fat Soluble o Absorption and transport closely associated with lipids Micelle enterocytes chylomicron lacteals o Stored in body lipids o Vitamins A D E K Minerals Inorganic Not energy yielding Element necessary for body functions which originates in the earth and cannot be made by Indestructible o Obtained from plant animal and soil o Content varies depending on the geographical location mineral content in soil Needed in larger quantities Ex calcium phosphorus potassium magnesium sodium chloride Needed in smaller quantities Ex copper zinc iodine fluorine iron selenium chromium manganese molybdenum Ultra trace found in the body in very small amounts harmful to body if there is too much o Arsenic boron nickel silicon vanadium cobolt Intake recommendations DRI recommendations to prevent chronic disease o RDA the avg daily amount of a nutrient considered adequate to meet the needs of most healthy people o AI number set if there is insufficient evidence to set an RDA Limits for specific age groups does not take into account metabolism activity illness or nourishment status UL max amount of a nutrient that appears safe for a healthy person to consume set to avoid toxicity Assessment of Intake Dietary assessment o Food intake records diary o Dietary recall o Food frequency questionnaire o Diet hx Lab tests o Blood work o Urinalysis o Hair analysis Physical assessment outward signs and symptoms ALCOHOL METABOLISM Dietary guidelines Drink in moderation o 2 drinks day for men o 1 drink day for women 1 drink provides oz of ethanol o 12 oz beer o 10 oz wine cooler o 5 oz wine o 1 5 oz liquor 80 proof o 1 oz liquor 100 proof Alcohol ethanol provides 7 kcal g Beverage Light beer Beer Craft and Microbrews Wine Coolers Wine Liquor 80 proof Liquor 100 proof Alcohol by volume ABV 4 5 5 6 6 4 6 9 12 40 50 How many calories of ETOH are in 12 oz beer that is 5 ABV 0 8g mL x ABV x volume of beverage mL grams of alcohol 0 8g mL x 5 x 360 mL 14 4 g ETOH 14 4g x 7 kcal 100 8 kcal Alcohol metabolism 3 systems o Alcohol dehydrogenase ADH o Microsomal Ethanol Oxidizing System MEOS o Catalase Alcohol dehydrogenase ADH o Located in Hepatocytes liver o Function Converts an alcohol into an aldehyde Requires NAD coenzyme niacin Gastric mucosal cells Women and those of Asian descent have less gastric mucosal cells and therefore make less ADH Reactions o Acetaldehyde Ethanol acetaldehyde Retinol predominantly in liver retinal vitamin A Can bind to proteins inhibiting factor includes enzymes Promotes fibrosis of liver leading to cirrhosis Toxic o Acetaldehyde dehydrogenase Located in liver Function Acetaldehyde acetate Requires NAD Problems with this pathway Saturation of enzymes Depletion of NAD o Summary Alcohol is converted into acetaldehyde by alcohol dehydrogenase which is released from the stomach and the liver This reaction requires NAD as a coenzyme Acetaldehyde is then converted into acetate by acetaldehyde dehydrogenase which also requires NAD and is released from the liver MEOS Microsomal Ethanol Oxidizing System o Location smooth endoplasmic reticulum SER o Works like Electron Transport Chain Utilizes riboflavin FAD and FMN and niacin NADPH not energy producing Cytochrome P450 protein o End products Water NADP Acetaldehyde o Inducible the more you drink tolerance Increases SER Increases P450 Bigger MEOS pathway A chronic drinker s MEOS will kick in quicker b c body has adapted o Metabolizes xenobiotics A large MEOS pathway will speed up the metabolism of drugs Leads to tolerance and possible toxicity xeno foreign o MEOS pathway bypasses alcohol dehydrogenase backup system Catalase Acetate acetyl CoA Denovo fatty acid synthesis FAs stay in liver enter blood via VLDL o 70 80 enters blood stream Signals decrease of FA s from adipose FA s that are released travel to liver Enters muscle tissue acetate acetyl CoA oxidized to energy Other metabolic changes in response to ethanol Body slows other metabolic processes to metabolize alcohol this is because ethanol is o Utilizes hydrogen peroxide o 2 of ethanol oxidation Acetate o 20 30 stays in liver toxic so it is metabolized first Gluconeogenesis declines Protein synthesis declines Krebs cycle slows o FA synthesis increases o Ketone formation increases High NADH NAD ratio Organ specific o GI tract o Pyruvate lactate lactate builds up when ingesting alcohol b c glucose is converted to pyruvate then lactate due to excess acetyl CoA need for NAD Stomach increased HCl secretions Acetaldehyde is toxic esp to mucosal cells Decreases intestinal absorption of almost all vitamins esp B vitamins Increased absorption of iron Increased risk of GI cancers heavy alcohol consumption tied to cancer Increased


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FSU HUN 3226 - Metabolism of Nutrients II

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