HNF 462 1st Edition Lecture 4 Outline of Last Lecture I. Deficiencya. Beriberib. MeasurementsII. Discovery and IsolationIII. FunctionsIV. Food Sources and StabilityV. Digestion, Absorption, and TransportationVI. ExcretionVII. RDAOutline of Current Lecture I. Discovery II. Sources and StructureIII. Digestion, Absorption, and TransportIV. ExcretionV. Functionsa. Electron Transport Chainb. Glutathione ReductaseVI. MeasurementVII. Deficiency and Toxicity a. Activity CoefficientsCurrent Lecture:1. Discoverya. Result of searching for additional essential factors after discovery of thiamin2. Food Sourcesa. Found in wide variety of foods: plant and animal sourcesb. Best sources are animal/dairy sources (B2 in form of FAD)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.3. Digestion, Absorption, and Transportationa. Digestion: by protein carriers, HCl, and peptidases; phosphatases used to digest and remove phosphate groupsb. Absorption: Inhibited by divalent metals and ethanoli. In the intestine: must by free of protein and phosphate groups; by active transport and Na-independent carriersii. Into the cells: free form transported into cells, then converted back to coenzyme forms (FMN/FAD) by adding back phosphate groups (done by enzyme flavokinase, which is regulated by hormones)c. Transportationi. Transported in blood mainly as riboflavin carried by proteins4. Excretiona. Excreted in the urine (Vitamin B2 gives urine yellow color)b. Decreased intake = decreased B2 in blood = decreased excretion5. Functions: Functions as coenzymes for many oxidative enzyme systems—remain bound to the enzymes during these redox reactions. Can act as oxidizing agents by accepting a pair of electrons. Reduced forms of riboflavin is found in FADH2.a. Electron Transport Chain: FADH2 travels through complex 2, and FMN acts as a coenzyme for complex 1b. PDHCc. Succinate Dehydrogenased. Acyl CoA Dehydrogenasee. B6f. Folateg. Niacinh. Glutathione Reductase (GR): reduces oxidized glutathione to reduced glutathione(recycles). Needs FADH2/FAD as a coenzyme, so if B2 is deficient, then won’t be fully functional6. Measurementa. Cellular levels of riboflavinb. Urinary Riboflavin excretion (increase intake = increase excretion)c. RBC glutathione reductase activity: most efficient way7. Deficiency and Toxicitya. Deficiencyi. Cellular riboflavin concentrations: <10 ug/dL ii. Urinary Excretion: <19 ug/g creatinine or <40 ug/day riboflavin1. Creatinine: product of creatine in muscles; removed from blood bythe kidneys and excreted in urine. A deficiency of vitamin will cause an increase in creatinine levelsiii. AC (“activity coefficients”) = enzyme activity + FAD/enzyme activity – FAD1. >1.2 indicates adequate levels2. <1.2 indicates deficiency b. Toxicity: No toxicity because it is water
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