Exam 1 Studyguide1. What’s the disease caused by vitamin C deficiency?- Scurvy 2. What are the reduced and oxidized forms of vitamin C?- The reduced form (you gained electrons) is ascorbic acid (can reduce iron and copper)- The oxidized form (you lost electrons) is dehydroascorbic acid3. How stable is vitamin C? What is it sensitive to? - Dehydroascorbic acid is less water soluble and not stable in water - Ascorbic acid is water soluble - Vitamin C is sensitive to heat, light, and oxygen - Can be partly or completely destroyed by long storage or cooking- Pasteurization destroys vitamin C4. Do all mammals need vitamin C from diet? - Not all mammals need vitamin C from diet - However: humans, other primates, fruit bats, guinea pigs, and some birds are unable to synthesize vitamin C5. What do most animals use to synthesize vitamin C? - Animals use glucose and produce L-ascorbate (ONLY THE L-FORM IS BIOLOGICALLY ACTIVE)6. What Na-dependent transporter is responsible for AA absorption? - SVCT1 and SVCT2 (sodium vitamin C transporter for ascorbic acid) - Dehydroascorbic acid is taken up by GLUT1 & GLUT3 7. Why are vitamin C deficient patients often iron deficient? - Ascorbic acid (vitamin C) enhances the intestinal absorption of nonheme ironbecause it reduces (ANTIOXIDANT) iron from ferric (Fe3+) to ferrous iron (Fe2+)- Only the ferrous (Fe2+) form is absorbed8. Which form of vitamin C is found in blood? - Ascorbic acid & dehydroascorbic acid (low concentration of DHAA)9. How are AA and DHAA absorbed by cells? What transporters do they use? - Ascorbic acid is transported by SVCT1 & SVCT2 into peripheral cells - Dehydroascorbic acid uses GLUT 1, 3, and 4 and is taken up by peripheral cells 10. AA transport into cells can happen against AA gradient. Why? - The SVCT1 & SVCT2 use the sodium gradient (from the NA/K pump) to drive ascorbic acid (vitamin C) into the cells 11. Know the synthetic reactions vitamin C participates in and the mechanism of vitamin C function in these reactions. - Collagen synthesis- hydroxylation reactions in collagen synthesis require vitamin C- Carnitine synthesis – hydroxylation reaction- Tyrosine synthesis and catabolism – hydroxylation reaction - Neurotransmitter synthesis: norepinephrine & serotonin- Generally, vitamin C functions as a reducing agent (antioxidant) to maintain the iron and copper atoms in the metalloenzymes in the reduced state.- In sum, vitamin C (antioxidant) functions in hydroxylase reactions by reducing iron and copper atoms 12. Why does curvy have hemorrhagic symptoms? - Vitamin C is important for the maintenance of connective tissues 13. How is vitamin C excreted? - Vitamin C is excreted in the urine - Reabsorbed by the kidney via SVCT1 - Excreted intact or various oxidized metabolites 14. Can vitamin C concentration in blood increase indefinitely in response to increased intake? Why? NO.- As vitamin C intake increases, plasma vitamin C increases until the kidney cannot reabsorb all the vitamin C present 15. High does vitamin C supplementation may increase the risk of kidney stones. Why? - Vitamin C (Ascorbic acid) can be oxidized to dehydroascorbic acid, which canbe broken down to harmful products such as oxalic acid- Oxalic acid forms calcium oxalate. These are not H20 soluble, so they can form kidney stones.16. What are free radicals? - Free radicals are reactive oxygen and nitrogen species - Generated by immune cells to destroy bacteria17. How does vitamin C decrease the risk of plaque formation and CVD? - Vitamin C (antioxidant) reduces LDL so that macrophages cannot take up the LDL (they normally take up oxidized LDL). This inhibits foam cell proliferation and plaque formation.18. Know the names of the B vitamins. For example, B1 is thiamin, B2 is riboflavin etc. - B1- thiamin - B2- riboflavin- B3- Niacin - B5- Pantothenic acid- B6- pyridoxal phosphate - B7- biotin - B9- folate - B12- cobalamin 19. What’s the disease caused by B1 deficiency? - Beriberi  means weakness 20. Know the four enzymes discussed in class that require B1 and what kind of reaction is catalyzed by these enzymes.- It is a coenzyme for oxidative decarboxylation of pyruvate/alpha ketoglutarate/ BCAAs/ transketolate in pentose phosphate pathway- Thiamin is required for thiamin pyrophosphate (TPP) which is an enzyme in the pyruvate dehydrogenase complex. - Transketolases in the pentose phosphate pathway require thiamin to transfer 2 carbons - The branched chain alpha-keto acid dehydrogenase requires thiamin for branched chain amino acid oxidative decarboxylation21. Is white rice or refined grain a good source of B1? How about brown rice? Why? - Vitamin is lost in the refining process - White rice is refined grain - Brown rice is a good source of vitamin B1 22. Which form of B1 is absorbed? Phosphorylated or unphosphorylated? Which enzyme removes P? - Free thiamin - Unphosphorylated - Phosphatase enzyme23. What form of riboflavin is absorbed by enterocytes and liver cells? - Na-independent carriers- ALWAYS free riboflavin via riboflavin-binding protein 24. What is riboflavin converted to once in the cells? - It is converted to FMN or FAD25. What’s the color of riboflavin? - Riboflavin is fluorescent yellow- it is excreted in the urine 26. What are the coenzyme forms of riboflavin? Are they both involved in ETC? - Coenzyme forms are FMN or FAD - Yes. FADH2 transports electrons to the ETC- FMN is a coenzyme for complex I 27. The activity of which enzyme in red blood cells is measured to assess riboflavin status? What is AC? - Red blood cell glutathione reductase activity - This enzyme requires FAD as a coenzyme - AC is the activity coefficient - The AC is 1.4 or greater, but if it is less it indicates low riboflavin28. What is the diseased caused by niacin deficiency? What is it associated with cornor maize based diet? - Pellagra- Corn is a poor source of niacin 29. What are the coenzyme forms of niacin? - NAD & NADP30. What form of niacin is absorbed? Are NADH and NADPH absorbed directly intact? - Nicotinamide and nicotinic acid - No. digestion is required.31. Is niacin transported as nicotinamide or nicotinic acid? Which one is the direct precursor of NAD and NADP? Which form is used to treat hypercholesterolemia? Which form causes niacin flush? - Transported primarily as nicotinamide, small amounts of nicotinic acid- Nicotinamide is the main precursor for NAD - Nicotinic acid causes niacin flush- Nicotinic acid is used to treat hypercholesterolemia