L51/52: Vitamin Deficiency Diseases Flashcards
(111 cards)
1
Q
What are the lipid-soluble vitamins?
A
A, D, E, and K
2
Q
What are the water-soluble vitamins?
A
C and B complex
3
Q
Which vitamins are only needed in microgram amounts?
A
Folic acid, vitamin K, vitamin D, and vitamin B12
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
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.
6
Q
What is beta-carotene a precursor for?
A
Retinal
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
8
Q
What is the RDA of vitamin A?
A
1000 retinol equivalents (corresponds to 1000 μg retinol or 6000 μg beta-carotene)
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
10
Q
What are the effects of deficiency of vitamin A?
A
Night blindness and keratinization of epithelial cells
11
Q
What does retinoic acid do?
A
Required for gene regulation and differentiation; not used in visual cycle
12
Q
Is excess vitamin A toxic?
A
Yes
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
14
Q
What does 11-cis retinal combine with? What does it form?
A
Combines w/ opsin to form rhodopsin, a visual pigment
15
Q
Where is vitamin A stored?
A
Retinol stored as retinyl esters mainly in liver and adipose tissues
16
Q
How is vitamin A transported?
A
Transported as retinyl esters by chylomicrons
17
Q
What receptors do all-trans reitnoic bind to?
A
RAR (retionic acid) receptors
18
Q
What receptors does 9-cis retinoic acid bind to?
A
RXR receptors
19
Q
What forms a dimer w/ RAR?
A
RXR
20
Q
What is vitamin B1 called?
A
Thiamine
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
22
Q
What is the effect of thiamine deficiency?
A
Beri-beri and Wernicke-Korsakoff syndrome. Polyneuritis, cardiac pathology, edema
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.
24
Q
What is wet Beri-Beri?
A
Caused by deficiency in thiamine. There is high-output cardiac failure (dilated cardiomyopathy) and edema
25
What is Wernicke-Korsakoff syndrome?
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.
26
Why is TPP not compatible w/ good absorption?
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.
27
What is another name for vitamin B2?
Riboflavin
28
What is the function of riboflavin?
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
29
What is the RDA for thiamine?
1.5 mg/day
30
What are sources of riboflavin?
Milk, liver, green vegetables
31
What is the RDA for riboflavin?
1.7 mg/day
32
What is the difference b/w FMN and FAD?
FAD has adenine attached to it from ATP.
33
What is the effect of riboflavin deficiency?
Skin lesions (this is seen in association w/ deficiency in many of the B vitamins)
34
What is vitamin B3 called?
Niacin
35
What is the function of niacin?
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.
36
What is the effect of deficiency of niacin?
Pellagra
37
What is Pellagra?
Deficiency of niacin. Have the 3 D's (dermatitis, diarrhea, dementia) and if severe, death.
38
What are sources of niacin?
Legumes, meat
39
What is the RDA of niacin?
19 mg/day. (only vitamin needed in large amounts is vitamin C)
40
How is NAD converted to NADP?
Addition of a single phosphate from ATP. Yet, end up w. a coenzyme that has a different role in cells.
41
What are the chief precursors for the synthesis of NAD and NADP?
Niacin and nicotinamide
42
Why does tryptophan have a niacin-sparing effect?
Because if you have a good source of tryptophan in the diet, don't need as much niacin.
43
What is the name of vitamin B5?
Pantothenic acid
44
What is the function of pantothenic acid?
Pantothenic acid is a precursor of pantotheine. This structure forms part of coenzyme A (CoA, a cofactor for acyl transfers) and fatty acid synthase.
45
What is the effect of pantothenic acid deficiency?
May be nausea and fatigue. A deficiency is practically unknown.
46
What is the RDA for pantothenic acid?
RDA has not been established. 5 - 10 mg/day might be used.
47
What are the sources of pantothenic acid?
Pantothenic acid is widely distributed and is synthesized by some intestinal bacteria (thus making deficiency unlikely)
48
What makes up Coenzyme 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
What is the name for vitamin B6?
Pyridoxine
50
What is the function of vitamin B6?
Pyridoxine (pyridoxol) is a precursor of pyridoxal phosphate (PLP) which is a coenzyme for enzymes catalyzing transamination, deamination, decarboxylation, and for glycogen phosphorylase.
51
What are sources of vitamin B6?
Liver, fish, nuts, whole grain cereals
52
What is the effect of deficiency of vitamin B6?
Dermatitis, convulsions, microcytic anemia
53
What is function of isoniazid?
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
What is the RDA for vitamin B6?
2 mg/day
55
What is vitamin B7 called?
Biotin (universally known as biotin)
56
What is the function of biotin?
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)
Propionyl-CoA carboxylase: propionyl-CoA (3C) to methylmalonyl-CoA (4C)
57
What are sources of biotin?
Intestinal microorganisms, liver, vegetables
58
What are effects of deficiency of biotin?
Dermatitis, anorexia, nausea, muscle pain
59
What is the RDA of biotin?
RDA not established
60
What can cause a deficiency of biotin?
Consumption of a large amount of raw eggs, which have avidin, wich tightly binds biotin and can result in poor biotin absorption
61
How/where does biotin attach to carboxylase enzymes?
Covalently links to lysine residue on the enzyme
62
What is vitamin B9 called?
Folate
63
What is the function of folate?
Folic acid is a precursor for tetrahydrofolate that is used as a carrier of one-carbon units at different levels of oxidation
64
What are the effects of deficiency of folate?
Megaloblastic anemia, GI disturbances; tissues most affected by this deficiency are those w/ rapid cell division (in bone marrow and GI tract)
65
What are sources of folate?
Intestinal bacteria, liver, yeast, and green vegetables
66
What is the RDA for folate?
400 μg/day
67
Why is maternal folic acid supplemented in early pregnancy?
To prevent neural tube defects
68
How is folic acid converted to tetrahydroflorate?
By the enzyme dihydrofolate reductase, which requires 2 NADP's
69
How do sulfanilamides act?
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
How does methotrexate act?
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
How does trimethoprim act?
Is an inhibitor for bacterial dihydrofolate reductase and not our dihydrofolate reductase. This is particularly used for bladder infections.
72
What is the folate trap?
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
What is vitamin B12 called?
Cobalamin
74
What is the chemical nature of vitamin B12?
B12 is a complex multiple ring structure which includes a cobalt atom
75
What is the function of vitamin B12?
Cofactor for tetrahydrofolate methyl transferase (transfers CH3 groups as methylcobalamin) and methylmalonyl CoA mutase
76
How if vitamin B12 absorbed?
Is absorbed from the ileum as a complex w/ intrinsic factor (IF) which is produced by parietal cells of the gastric mucosa
77
What are the effects of vitamin B12 deficiency?
Pernicious anemia and degradation of spinal cord neurons
78
What are the sources of vitamin B12?
Meat and milk (vegans are at risk for deficiency)
79
What is the RDA for vitamin B12?
3 μg/day (this is the vitamin that we need the least amount of)
80
In a commercial multivitamin, what form is B12 taken in?
Cyanocobalmin
81
Why is there accumulation of fatty acids w/ odd branch structure when there is B12 deficiency?
Because Methylmalonyl-CoA mutase isn't converting methylmalonyl CoA to succinylCoA
82
What is vitamin C also called?
Acorbic acid
83
Can humans make vitamin C?
No
84
What is the function of vitamin C?
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
What is the effect of vitamin C deficiency?
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
What are sources of vitamin C?
Fruits and vegetables
87
What is the RDA for vitamin C?
60 mg/day (this is the highest of the vitamins)
88
What is the risk of mega-dosing of ascorbic acid?
Would get conversion of it to oxalate, which would increase risk of kidney stones
89
How does vitamin C act as an antioxidant?
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
What is the function of vitamin D?
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
What are sources of vitamin D?
UV irradiation of 7-dehydrocholesterol in the skin, fish liver oils and supplemented milk
92
What are the effects of deficiency of vitamin D?
Rickets and osteomalacia
93
What is rickets?
Occurs in children. They continue to get bone growth but it is poorly mineralized and get collagen deposition. Get bone pain and deformity.
94
What is osteomalacia?
Occurs in adults; there is demineralization of bones that results in brittle bones that are more likely to break
95
What is the RDA for vitamin D?
600 international units (15 μg cholecalciferol)
96
What form is the vitamin D ingested from plants?
Ergocalciferol
97
What is the active metabolite of vitamin D?
1,25-dihydroxycholecalciferol; this is the form that binds to vitamin D receptors and key target tissues are bone, intestine and kidney
98
How do you get active 1,25-dihydroxycholecalcierol from vitamin D3?
Hydroxylation at 25 position (occurs in liver) and hydroxylation at 1 position (occurs in kidney)
99
What are the effects of 1,25 D3 on bone?
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
What is vitamin E called?
Tocopherol
101
What is the function of vitamin E?
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
What is the effect of deficiency of vitamin E?
Associated w/ lysis of erythroyctes
103
What is the source of vitamin E?
Vegetables and wheat germ oil
104
What is the RDA for vitamin E?
15 international units. Greater amounts may be beneficial but there is conflicting data.
105
What is the major form of vitamin E? What does it do?
α-tocopherol is the major form and serves as an antioxidant. Can be reduced back by both ascorbate and glutathione
106
What is the function of vitamin K?
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
What is the effect of deficiency of vitamin K?
Deficiency is rare but can be associated w/ prolonged blood clotting times
108
What are the sources of vitamin K?
Produced by intestinal bacteria
109
What is the RDA for vitamin K?
No RDA has been established, but 70 - 140 μg may be appropriate
110
What are some general RDA's for vitamins?
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
What are the effects of excess of vitamin D?
Hypercalcemia, hypercalciuria, loss of appetite, stupor. Seen in granulomatous disease.
