Water-Soluble Vitamins Study Guide
Water-Soluble Vitamins Study Guide NUTRITN 230
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This 4 page Study Guide was uploaded by Juliana Bernard on Wednesday January 28, 2015. The Study Guide belongs to NUTRITN 230 at a university taught by Dr. Ronnenberg in Fall. Since its upload, it has received 560 views.
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Date Created: 01/28/15
WATERSOLUBLE VITAMINS STUDY GUIDE WaterSoluble thiamin riboflavin niacin pantothenic acid biotin vitamin BG vitamin B12 folate vitamin C FatSoluble Vitamins A D E K B1 Thiamin TPP Thiamin is an important participant in many energyyielding reactions Thiamin39s coenzyme form TPP participates in decarboxylation which removes a carboxyl group and releases it at carbon dioxide These reactions can be found taking place when converting pyruvate to acetyl CoA and also during the citric acid cycle TPP also plays a role in nerve function thiamin might regulate the movement of chemicals involved in the transmission of messages throughout the nervous system Needed in synthesis of acetylcholine Sources of thiamin include total cereal enriched rice pork ham lentils legumes RDA 11 12 mgday Deficiency beriberi first signs are weakness irritability headache fatigue and depression As symptoms progress dry beriberi beriberi without edema causes nerve degeneration loss of nerve transmission leading to tingling sensations throughout the body muscle wasting poor arm and leg coordination and deep pain in calf muscles Wet beriberi has additional symptoms including enlarged heart heart failure and severe edema Thiamin deficiency is related to heavy alcohol consumption combined with limited food consumption alcohol interferes with absorption of thiamin and other vitamins No upper limit toxicity risk is very low 32 Riboflavin FAD FMN Named for it39s yellow color Destroyed by heat and UV rays Riboflavin vitamin accepts and donates electrons with ease so it participates in many oxidationreduction reac ons Part of 2 coenzymes FAD and FMN These coenzymes participate in numerous metabolic pathways including the citric acid cycle and the betaoxidation pathway that breaks down fatty acids FMN and FAD act first as electron and hydrogen acceptors forming reduced forms Riboflavincontaining enzymes participate in reactions that remove ammonia during the deamination of some amino acids Help protect RBCs and other cells from oxidative stress Sources of riboflavin include milkmilk products eggs meats legumes total cereal fruits veggies RDA 11 13 mgday Deficiency ariboflavinosis tongue gets shiny smooth and inflamed glossitis the mouth becomes painful and sore the skin at the corners of mouth cracks angular stomatitis and the lips become inflamed and split cheilosis Riboflavin deficiencies are rare but because it is involved in metabolism of other B vitamins severe riboflavin deficiency can make other deficiencies even worse Toxicity has not been reported 3 Niacin NAD NADP Niacin is the name for two similarly functioning compounds nicotinic acid and nicotinamide NAD and NADP play important roles in oxidationreduction reactions NAD accepts electrons and hydrogen is reduced to form NADH Under anaerobic conditions NADH carries highenergy electrons to the electron transport chain to help produce ATP ln anaerobic conditions NADH powers conversion of pyruvate to lactate as it loses electrons and a hydrogen is oxidized to become NAD which helps power glycolysis NADPH reduced form of NADP is relied on for synthesis of fatty acids and amino acids Sources of niacin include chicken total cereal trout meat RDA 16 14 mg of NEday 60 mg tryptophan yields 1 mg niacin Deficiency pellagra 4 D39s dermatitis red skin around neck arms etc and roughened skin dementia nerve damage paralysis anxiety depression weakness diarrhea gastrointestinal lesions and death In cereal grains niacin may be bound to complex carbohydrates nyacytin or small peptides niacinogens treatment with base alkali releases niacin in these complexes A protein in corn binds niacin tightly reducing it39s bioavailability so soaking the corn in solution of lime released the bound niacin Uses high doses of nicotinic acid are used to treat elevated blood lipids lowers triglycerides nicotinamide may delay onset of type DM in person showing early signs High doses of niacin may cause flushing of skin tingling sensation rashes nausea liver abnormalities blurred vision Pantothenic Acid CoA acetyl coA acyl carrier protein Pantothenic acid is a component of coenzyme A which in turn is a component of acetyl CoA Acetyl CoA is in number of metabolic pathways both energygenerating and biosynthetic it is formed from pyruvate starts the citric acid cycle is a key building block of fatty acids and is precursor of ketone bodies During fatty acid synthesis acyl carrier protein binds fatty acids and carries hem through a series of reactions that increases their chain length Pantothenic acid is widespread in food supply specific sources known include chicken beef potatoes oats egg yolk total cereal Deficiency are virtually nonexistent in the general population but when induced symptoms included irritability restlessness fatigue apathy malaise sleep disturbances nausea numbness and hypoglycemia Risk of toxicity is extremely low No RDA Al 5 mg day Biotin n food biotin is found both free and bound to protein when digested biocytin is released Biotin acts as a coenzyme in many reactions amino acid metabolism conversion of amino acids to glucose gluconeogenesis fatty acid synthesis release of energy from fatty acids and DNA synthesis Biotincontaining enzymes mainly catalyze carboxylation reactions serves as a carboxyl adds C02 carrier Pyruvate can be carboxylated to oxaloacetate Sources of biotin include cauliflower liver peanuts cheese and egg yolk Avidin in raw egg whites binds biotin and prevents absorption from raw eggs No RDA Al 30 microgramsday Deficiency very rare unless eating mass amounts of raw egg whites deficiency could cause initial hair loss rash convulsions neurological disorders changes blood pH if untreated Toxicity is very rare Folate Folate and B12 work together in many biochemical functions Folate refers to a group of several closely related folate forms differing in the number of glutamates attached Folic acid monoglutamate most stable form easiest to absorb Folate polyglutamate must be hydrolyzed into monoglutamate form before absorption As a coenzyme folate is crucial to DNA synthesis and cell division amino acid metabolism and the maturation of red blood cells and other cells very important in growth and is crucial in early pregnancy to reduce birth defect called neural tube defects NTDs Body converts folate to coenzyme THFA which has 5 active forms Bioavailability of folate varies depending on stomach contents the folate form and alcohol presence RDA 400 micrograms of DFE day 600 micrograms of DFE day during pregnancy and 500 micrograms day when breastfeeding Sources of folate include total cereal leafy greens beans seeds nuts Folate deficiency can lead to anemia atherosclerosis NTDs birth defects and neuropsychiatric disorders Deficiency can stem from nadequate folate consumption causes folate deficiency nadequate folate absorption results from abnormalities in mucosal cells lining GI tract ncreased folate requirements mpaired folate utilization typically associated with vitamin BG deficiency Altered folate metabolism alcohol use Folate has important role in preventing heart disease folate B12 and BG work together to reduce elevated homocysteine Folate is needed in order for cells to divide without folate RBCs cannot grow or divide normally so they form large fragile immature cells called megaloblasts a hallmark of megaloblastic anemia Megaloblasts can mature into macrocytes NTDs neural tube fails to encase the spinal cord during early fetal development causing spina bifida and anencephaly Folate is connected to cancer when someone has the beginning of cancer adding folic acid feeds baby cancers Folate can mask B12 deficiency and consuming excess folate can prevent the formation of altered red blood cells that signals a lack of B12 UL is 1000 micrograms day Vitamin B12 Group of cobaltcontaining compounds known collectively as cobalamin Obtained entirely from animal sources Plays a key role in folate metabolism by transferring a methyl group from the folate coenzyme THFA turning folate into its active form B12 also helps maintain myelin sheath that surrounds nerve fibers Helps rearrange carbon atoms in fatty acid chains to prepare them to enter citric acid cycle Absorbing vitamin B12 requires several factors in the stomach B12 binds with Rprotein produced by salivary glands that protects it as it travels through stomach and intestine In small intestine pancreatic proteases cleave it from the Rprotein and B12 then binds to intrinsic factor produced by parietal cells and then travels to the ileum and attach to receptor cells on the BBM Receptor cells absorb B12 and transfer it to a protein carrier in the blood which enters the bloodstream and delivers B12 to the liver bone marrow and developing blood cells As people get older parietal cells make less and less HCI and intrinsic factor Because it is absorbed in ileum many surgeries can cause issues with this absorption Sources of B12 include beef liver salmon fortified cereals milk milk products RDA 24 micrograms day Deficiency we can store enough B12 in the liver to last years so symptoms may take around 6 years to show Vegans are at high risk if they don39t seek out supplements Prevalence for deficiency increases with age Most deficiencies esp in elderly is caused by inadequate intake or impaired absorption Major outcome of impaired absorption is vitamin B12deficiency anemia as in folate deficiency anemia lack of B12 causes formation of megaloblasts and macrocytes rather than normal RBCs B12 deficiency causes myelin sheath to swell and break down leading to brain abnormalities and spinal cord degeneration tingling numbness abnormal gait cognitive changes Pernicious anemia result of autoimmune disorder when body destroys parietal cells in stomach resulting in loss of intrinsic factor High levels of B12 from food or supplements have not been shown to cause harmful side effects Vitamin Be Term used for 3 forms pyridoxine PN pyridoxal PL PLP is the active coenzyme form pyridoxamine PM All have a phosphate derivative Pyridoxine hydrochloride is the form of Be usually used for food fortification and pharmaceutical preparations high bioavailability Pyridoxine as PLP is a coenzyme in gt 100 enzymes involved in energy metabolism including glycogen It is particularly important in synthesis of nonessential amino acids from other amino acids transaminations Also needed for decarboxylation reactions involved in the synthesis of neurotransmitters and other substances such as tryptophan to serotonin histidine to histamine Needed for synthesis of the protein heme which is an essential component of hemoglobin Serves as a coenzyme in many reactions involved in amino acid metabolism Widely distributed in food best sources include bananas legumes walnuts meat fish poultry RDA 13 mgday for men and women lt 50 years Deficiency is uncommon but has occurred in babies fed BGdeficient formula Suboptimal BG status may be common among adults Deficiency symptoms include depression weakness headaches confusion tingling and seizures and also results in Diminished immune function and impaired learning in offspring of BGdeficient women Anemia hypochromic microcytic due to reduced heme synthesis lmpaired transsulfuration of methionine to cysteine leading to elevated blood levels of homocysteine Excessive BG supplementation 16 gday can result in severe nerve impairment peripheral neuropathy lntake ideally lt 100 mgday wmmmc Ascorbic acid Water soluble antioxidant Most species synthesize vitamin C however we lack final enzyme Lgulonolactone oxidase so humans cannot Func ons Collagen synthesis collagen is the main structural protein in skin connective tissue bone and other body components Vitamin C is needed for the hydroxylation of proline and lysine molecules in the collagen peptide to hydroxyproline and hydroxylysine which are needed to form the collagen cross links that stabilize and strengthen the collagen molecule Without Vitamin C collagen is unable to crosslink resulting in poor wound healing ruptured capillaries etc Carnitine synthesis needed for LCFA to be oxidized Neurotransmitter synthesis norepinephrine and serotonin synthesis require vitamin C linked to depression Bile acid synthesis helps modulate an important liver enzyme involved in cholesterol conversion to bile acids Vitamin C protects DNA against free radicals Vitamin C is an antioxidant operating in body fluids to protect lipids in the blood DNA white blood cells the lining of the lungs and the stomach mucosa Free radicals can damage DNA and other molecules vitamin C neutralizes free radicals so they can no longer damage molecules like DNA Evidence on the common cold question is contradictory but it may slightly reduce the duration and intensity High vitamin C intake is correlated with a lower risk of many diseases including cancer of the mouth larynx and esophagus may also help prevent heart disease by preventing oxidative damage to lipoproteinsarteries and by lowering LDL levels RDA 90 mgday Food sources fruits and fruitjuices particularly citrus fruits watermelon cantaloupe kiwi and mango vegetables such as broccoli bell peppers spinach and green beans potatoes and sweet potatoes vitamin C is vulnerable to heat and light Vitamin C is essentially nontoxic excess amounts removed from body fluids promptly however excessive supplemental doses can cause unpleasant side effects such as diarrhea nausea abdominal cramps
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