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MCS > L51/52: Vitamin Deficiency Diseases > Flashcards

L51/52: Vitamin Deficiency Diseases Flashcards

1
Q

What are the lipid-soluble vitamins?

A

A, D, E, and K

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2
Q

What are the water-soluble vitamins?

A

C and B complex

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3
Q

Which vitamins are only needed in microgram amounts?

A

Folic acid, vitamin K, vitamin D, and vitamin B12

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4
Q

What are the dietary sources of vitamin A?

A

Vegetables, fish liver oil, polar bear liver. Retinyl esters and retinol are found in certain animal tissues. B-carotenes are found in certain plants

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5
Q

What is the function of vitamin A?

A

Retinol is a precursor for retinal that is used in the visual cycle and for retinoic acid that is required for maintenance of epithelial cells. In the visual cycle, opsin binds the 11-cis isomer of retinal. Light causes the conversion of all-trans isomer which is only weakly bound to opsin.

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6
Q

What is beta-carotene a precursor for?

A

Retinal

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7
Q

What form of retinoid is used in vision and detecting light?

A

11-cis retinal; this is converted to all-trans retinal by photoisomerization

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8
Q

What is the RDA of vitamin A?

A

1000 retinol equivalents (corresponds to 1000 μg retinol or 6000 μg beta-carotene)

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9
Q

Why do you need to consume more beta-carotene (rather than retinol) if only getting vitamin A in that form?

A

Conversion of Beta-carotene to retinol and retinal is not that efficient

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10
Q

What are the effects of deficiency of vitamin A?

A

Night blindness and keratinization of epithelial cells

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11
Q

What does retinoic acid do?

A

Required for gene regulation and differentiation; not used in visual cycle

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12
Q

Is excess vitamin A toxic?

A

Yes

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13
Q

What results from vitamin A toxicity?

A

Acute toxicity - nausea, vomiting, vertigo, and blurred vision
Chronic toxicity - alopecia, dry skin (scaliness), hepatic toxicity and enlargement, increased intracranial pressure

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14
Q

What does 11-cis retinal combine with? What does it form?

A

Combines w/ opsin to form rhodopsin, a visual pigment

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15
Q

Where is vitamin A stored?

A

Retinol stored as retinyl esters mainly in liver and adipose tissues

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16
Q

How is vitamin A transported?

A

Transported as retinyl esters by chylomicrons

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17
Q

What receptors do all-trans reitnoic bind to?

A

RAR (retionic acid) receptors

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18
Q

What receptors does 9-cis retinoic acid bind to?

A

RXR receptors

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19
Q

What forms a dimer w/ RAR?

A

RXR

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20
Q

What is vitamin B1 called?

A

Thiamine

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21
Q

What is the function of thiamine?

A

Thiamine is converted to thiamine pyrophosphate (TPP) which is a cofactor for: 1) pyruvate dehydrogenase (links glycolysis to TCA cycle), 2) α-ketoglutarate dehydrogenase (TCA cycle), 3) transketolase (pentose phosphate pathway), and 4) branched-chain ketoacid dehydrogenase

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22
Q

What is the effect of thiamine deficiency?

A

Beri-beri and Wernicke-Korsakoff syndrome. Polyneuritis, cardiac pathology, edema

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23
Q

What is dry Beri-Beri?

A

Condition caused by deficiency in thiamine. Such as when there is a transition in diet from whole-grain rice to white rice. Results in polyneuritis and symmetrical muscle wasting.

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24
Q

What is wet Beri-Beri?

A

Caused by deficiency in thiamine. There is high-output cardiac failure (dilated cardiomyopathy) and edema

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25
Q

What is Wernicke-Korsakoff syndrome?

A

Caused by deficiency in thiamine. Seen in alcoholics since they get a lot of calories from alcoholic drinks and there isn’t much thiamine there. There are GI tract disturbances. Also encephalopathy and psychiatric features. Classic triad is confusion, opthalmoplegia, and ataxia.

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26
Q

Why is TPP not compatible w/ good absorption?

A

TPP has charges on phosphate groups and is thus not compatible with good absorption. Body is better able to absorb thiamine from the gut, which can then be phosphorylated using ATP to form TPP.

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27
Q

What is another name for vitamin B2?

A

Riboflavin

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28
Q

What is the function of riboflavin?

A

Precursor for the coenzymes FMN and FAD. FMN is in complex I of the ETC. FAD is an important coenzyme for succinate dehydrogenase in the TCA cycle, mitochondrial glycerol phosphate dehydrogenase, in fatty acid oxidation

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29
Q

What is the RDA for thiamine?

A

1.5 mg/day

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30
Q

What are sources of riboflavin?

A

Milk, liver, green vegetables

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31
Q

What is the RDA for riboflavin?

A

1.7 mg/day

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32
Q

What is the difference b/w FMN and FAD?

A

FAD has adenine attached to it from ATP.

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33
Q

What is the effect of riboflavin deficiency?

A

Skin lesions (this is seen in association w/ deficiency in many of the B vitamins)

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34
Q

What is vitamin B3 called?

A

Niacin

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35
Q

What is the function of niacin?

A

As nicotinic acid or nicotinamide, it is a precursor for the coenzymes NAD and NADP. Is derived from tryptophan. Synthesis requires vitamins B2 and B6.

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36
Q

What is the effect of deficiency of niacin?

A

Pellagra

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37
Q

What is Pellagra?

A

Deficiency of niacin. Have the 3 D’s (dermatitis, diarrhea, dementia) and if severe, death.

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38
Q

What are sources of niacin?

A

Legumes, meat

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39
Q

What is the RDA of niacin?

A

19 mg/day. (only vitamin needed in large amounts is vitamin C)

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40
Q

How is NAD converted to NADP?

A

Addition of a single phosphate from ATP. Yet, end up w. a coenzyme that has a different role in cells.

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41
Q

What are the chief precursors for the synthesis of NAD and NADP?

A

Niacin and nicotinamide

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42
Q

Why does tryptophan have a niacin-sparing effect?

A

Because if you have a good source of tryptophan in the diet, don’t need as much niacin.

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43
Q

What is the name of vitamin B5?

A

Pantothenic acid

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44
Q

What is the function of pantothenic acid?

A

Pantothenic acid is a precursor of pantotheine. This structure forms part of coenzyme A (CoA, a cofactor for acyl transfers) and fatty acid synthase.

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45
Q

What is the effect of pantothenic acid deficiency?

A

May be nausea and fatigue. A deficiency is practically unknown.

46
Q

What is the RDA for pantothenic acid?

A

RDA has not been established. 5 - 10 mg/day might be used.

47
Q

What are the sources of pantothenic acid?

A

Pantothenic acid is widely distributed and is synthesized by some intestinal bacteria (thus making deficiency unlikely)

48
Q

What makes up Coenzyme A?

A

There is adenine. Business end of CoA which has sulfhydryl groups is from cysteine. Pantothenic part cannot be synthesized by us and must get it from the diet or from intestinal bacteria

49
Q

What is the name for vitamin B6?

A

Pyridoxine

50
Q

What is the function of vitamin B6?

A

Pyridoxine (pyridoxol) is a precursor of pyridoxal phosphate (PLP) which is a coenzyme for enzymes catalyzing transamination, deamination, decarboxylation, and for glycogen phosphorylase.

51
Q

What are sources of vitamin B6?

A

Liver, fish, nuts, whole grain cereals

52
Q

What is the effect of deficiency of vitamin B6?

A

Dermatitis, convulsions, microcytic anemia

53
Q

What is function of isoniazid?

A

It is a drug for treatment of TB. Has a vitamin B6 antagonistic role and there is danger of vitamin B6 deficiency in treatment w/ isoniazid

54
Q

What is the RDA for vitamin B6?

A

2 mg/day

55
Q

What is vitamin B7 called?

A

Biotin (universally known as biotin)

56
Q

What is the function of biotin?

A

Acts as a coenzyme in carboxylation reactions (which add a 1-carbon group) in covalent linkage to lysine side chains of enzymes. Pyruvate carboxylase: pyruvate (3C) to oxaloacetate (4C),
Acetyl-CoA carboxylase: acetyl-CoA (2C) to malonyl-CoA (3C)
ƒƒPropionyl-CoA carboxylase: propionyl-CoA (3C) Ž to methylmalonyl-CoA (4C)

57
Q

What are sources of biotin?

A

Intestinal microorganisms, liver, vegetables

58
Q

What are effects of deficiency of biotin?

A

Dermatitis, anorexia, nausea, muscle pain

59
Q

What is the RDA of biotin?

A

RDA not established

60
Q

What can cause a deficiency of biotin?

A

Consumption of a large amount of raw eggs, which have avidin, wich tightly binds biotin and can result in poor biotin absorption

61
Q

How/where does biotin attach to carboxylase enzymes?

A

Covalently links to lysine residue on the enzyme

62
Q

What is vitamin B9 called?

A

Folate

63
Q

What is the function of folate?

A

Folic acid is a precursor for tetrahydrofolate that is used as a carrier of one-carbon units at different levels of oxidation

64
Q

What are the effects of deficiency of folate?

A

Megaloblastic anemia, GI disturbances; tissues most affected by this deficiency are those w/ rapid cell division (in bone marrow and GI tract)

65
Q

What are sources of folate?

A

Intestinal bacteria, liver, yeast, and green vegetables

66
Q

What is the RDA for folate?

A

400 μg/day

67
Q

Why is maternal folic acid supplemented in early pregnancy?

A

To prevent neural tube defects

68
Q

How is folic acid converted to tetrahydroflorate?

A

By the enzyme dihydrofolate reductase, which requires 2 NADP’s

69
Q

How do sulfanilamides act?

A

They were used to treat bacterial infections before discovery of naturally occurring antibiotics. The structure resembles that of PABA and thus acts to inhibit formation of folic acid by bacteria

70
Q

How does methotrexate act?

A

Is an inhibitor of dihydrofolatereductase, which means that there are inadequate amounts for making various building blocks. If things go as hoped, have tolerable activity for normal cells and fatal toxicity for cancer cells. This has particularly been used for treatment of leukemia. Also used in psoriasis, another proliferative state.

71
Q

How does trimethoprim act?

A

Is an inhibitor for bacterial dihydrofolate reductase and not our dihydrofolate reductase. This is particularly used for bladder infections.

72
Q

What is the folate trap?

A

There is potential for folate to be trapped in the form of Methyl-THF in the case of B12 deficiency because is required for the irreversible reaction of homocysteine to methionine. In absence of B12, get accumulation of Methyl-THF since this is irreversible and the rest of the reactions are irreversible, so all THF becomes bound as Methyl-THF.

73
Q

What is vitamin B12 called?

A

Cobalamin

74
Q

What is the chemical nature of vitamin B12?

A

B12 is a complex multiple ring structure which includes a cobalt atom

75
Q

What is the function of vitamin B12?

A

Cofactor for tetrahydrofolate methyl transferase (transfers CH3 groups as methylcobalamin) and methylmalonyl CoA mutase

76
Q

How if vitamin B12 absorbed?

A

Is absorbed from the ileum as a complex w/ intrinsic factor (IF) which is produced by parietal cells of the gastric mucosa

77
Q

What are the effects of vitamin B12 deficiency?

A

Pernicious anemia and degradation of spinal cord neurons

78
Q

What are the sources of vitamin B12?

A

Meat and milk (vegans are at risk for deficiency)

79
Q

What is the RDA for vitamin B12?

A

3 μg/day (this is the vitamin that we need the least amount of)

80
Q

In a commercial multivitamin, what form is B12 taken in?

A

Cyanocobalmin

81
Q

Why is there accumulation of fatty acids w/ odd branch structure when there is B12 deficiency?

A

Because Methylmalonyl-CoA mutase isn’t converting methylmalonyl CoA to succinylCoA

82
Q

What is vitamin C also called?

A

Acorbic acid

83
Q

Can humans make vitamin C?

A

No

84
Q

What is the function of vitamin C?

A

Ascorbic acid is a water-soluble antioxidant and it promotes the hydroxylation of proline residues of collagen. Ascorbic acid is also required in the synthesis of carnitine, dopamine, and bile acids.

85
Q

What is the effect of vitamin C deficiency?

A

Scurvy (hemorrhage, impaired wound healing and bone formation); caused by improper maturation of collagen b/c don’t properly hydroxylate proline residues of collagen to form mature form of collagen

86
Q

What are sources of vitamin C?

A

Fruits and vegetables

87
Q

What is the RDA for vitamin C?

A

60 mg/day (this is the highest of the vitamins)

88
Q

What is the risk of mega-dosing of ascorbic acid?

A

Would get conversion of it to oxalate, which would increase risk of kidney stones

89
Q

How does vitamin C act as an antioxidant?

A

Ascorbate gets converted to dehydroascorbic acid after it neutralizes reactive oxygens. It can be re-converted to ascorbate by reduced glutathione which becomes oxidizes in the process.

90
Q

What is the function of vitamin D?

A

Regulation of calcium levels through actions on intestine, kidney, and bone. Vitamin D3 (cholecalciferol) requires conversion to 1,25-dihydroxy vitamin D3 to form the active compound.

91
Q

What are sources of vitamin D?

A

UV irradiation of 7-dehydrocholesterol in the skin, fish liver oils and supplemented milk

92
Q

What are the effects of deficiency of vitamin D?

A

Rickets and osteomalacia

93
Q

What is rickets?

A

Occurs in children. They continue to get bone growth but it is poorly mineralized and get collagen deposition. Get bone pain and deformity.

94
Q

What is osteomalacia?

A

Occurs in adults; there is demineralization of bones that results in brittle bones that are more likely to break

95
Q

What is the RDA for vitamin D?

A

600 international units (15 μg cholecalciferol)

96
Q

What form is the vitamin D ingested from plants?

A

Ergocalciferol

97
Q

What is the active metabolite of vitamin D?

A

1,25-dihydroxycholecalciferol; this is the form that binds to vitamin D receptors and key target tissues are bone, intestine and kidney

98
Q

How do you get active 1,25-dihydroxycholecalcierol from vitamin D3?

A

Hydroxylation at 25 position (occurs in liver) and hydroxylation at 1 position (occurs in kidney)

99
Q

What are the effects of 1,25 D3 on bone?

A

It actually increases bone solubilization (counter intuitive); other effects raise blood calcium levels by increasing calcium absorption in the intestine and decreasing calcium excretion in the kidneys; overall, get increased mineralization of bone

100
Q

What is vitamin E called?

A

Tocopherol

101
Q

What is the function of vitamin E?

A

Vitamin E (tocopherol) is a lipid-soluble antioxidant and helps to prevent lipid damage. Particularly important for maintenance of membrane integrity. Protects them from free radical damage.

102
Q

What is the effect of deficiency of vitamin E?

A

Associated w/ lysis of erythroyctes

103
Q

What is the source of vitamin E?

A

Vegetables and wheat germ oil

104
Q

What is the RDA for vitamin E?

A

15 international units. Greater amounts may be beneficial but there is conflicting data.

105
Q

What is the major form of vitamin E? What does it do?

A

α-tocopherol is the major form and serves as an antioxidant. Can be reduced back by both ascorbate and glutathione

106
Q

What is the function of vitamin K?

A

A coenzyme for the carboxylation of glutamic acid side chains of some blood clotting factors (prothrombin, factors VII, IX and X). Has role in modifcation of proteins where there is gamma-carboxylation of side chains such that you get a group that is nice for binding calcium. This is important for calcium-binding blood clotting factors

107
Q

What is the effect of deficiency of vitamin K?

A

Deficiency is rare but can be associated w/ prolonged blood clotting times

108
Q

What are the sources of vitamin K?

A

Produced by intestinal bacteria

109
Q

What is the RDA for vitamin K?

A

No RDA has been established, but 70 - 140 μg may be appropriate

110
Q

What are some general RDA’s for vitamins?

A

Multi-mg for vitamin C and niacin; 1-2 mg/day for vitamin A, thiamine, riboflavin, and pyridoxine; high microgram amounts for folic acid; low microgram amounts for vitamin D and B12

111
Q

What are the effects of excess of vitamin D?

A

Hypercalcemia, hypercalciuria, loss of appetite, stupor. Seen in granulomatous disease.

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