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Biochemistry: Block 4 > Vitamins > Flashcards

Vitamins Flashcards

1
Q

What is a vitamin?

A

An organic micronutrient that cannot be synthesized in adequate quantities in humans and must be supplied by the diet

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2
Q

What are the four functional classes of vitamins?

A

Coenzymes, free-radical scavengers, photopigments, hormone-like transcription factors

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3
Q

What is the common name for Vitamin B9?

A

Folic Acid

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4
Q

What processes is folate critical for?

A

Synthesis of amino acids, purines, thymidine

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5
Q

What is sulfonamide’s mechanism of action?

A

Competative inhibition of dihydropteroate synthase which is involved in synthesis of folate

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6
Q

What is methotrexate’s mechanism of action?

A

Inhibition of dihydrofolate reductase

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7
Q

What are the three major fates of THF?

A

Amino Acid synthesis (esp. Methionine); purine biosynthesis; thiamine biosynthesis

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8
Q

What is the most common vitamin deficiency in America and Europe?

A

Folate (B9)

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9
Q

What are the two main systemic functions for folate?

A

Nucleotide biosynthesis and DNA methylation in the cytoskeleton

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10
Q

What will folate deficiency lead to in adults?

A

Downregulation of DNA synthesis–> megaloblastic anemia , neuropathy

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11
Q

How does folate deficiency lead to neuropathies?

A

Destabilization of cytoskeletal elements

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12
Q

What developmental defect can result as a consequence of folate deficiency?

A

Spina bifida

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13
Q

What is the functional form of B9 vitamin?

A

THF

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14
Q

How does folate deficiency contribute to the onset of megaloblastic anemia?

A

DNA synthesis is inhibited, but stem cells in the bone marrow continue to divide. The cells accumulate fragmented chromosomes and end up with polyploidy nuclei

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15
Q

What is the diagnostic feature of folate deficiency?

A

Megaloblastic anemia

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16
Q

What is the physical difference between anemia caused by iron defiency and by folate deficincy?

A

Iron defiecincy anemia results in small cell size- Microcytic; folate deficincy anemia causes large RBC size

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17
Q

Why can excess folate be problematic?

A

It can mask a Vitamin B12 deficiency

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18
Q

What is the common name of Vitamin B12?

A

Cobalamin

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19
Q

What are the active forms of vitamin B12?

A

Deoxyadenosyl cobalamin and methyl cobalamin

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20
Q

For what processes is cobalamin required?

A

Methionine biosynthesis, isomerization of methylmalonyl CoA to Succinyl CoA, fatty acid catabolism

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21
Q

How is cobalamin absorbed?

A

Cobalamin binds to intrinsic factor secreted by stomach parietal cells, which binds to intrinsic factor receptors in the ileum

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22
Q

What is the connection between Vitamins B9 and B12?

A

Methionine Synthase recycles 5-methyl THF to THF using cobalamin as a factor

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23
Q

What processes are inhibited with cobalamin deficiency?

A

Methylation and purine synthesis

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24
Q

How does a vitamin B12 deficiency result in neuropathies?

A

Methionine synthase uses the methylated form of cobakamin as a methyl donor for homocysteine–> methionine; no SAM is produced–> no methylation

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25
Q

How does a vitamin B12 deficiency result in megaloblastic anemia?

A

No recycling of 5-methyl THF–> THF; inhibition of Met (SAM) synthesis

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26
Q

What are the most common causes of cobalamin deficiency?

A

Autoimmune atrophic gastritis; gastrectomy; age

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27
Q

What is the comon name for Vitamin C?

A

Ascorbic Acid

28
Q

What vitamin serves as a coenzyme in hydroxylation reactions?

A

Vitamin C

29
Q

What is vitamin C’s main role in the body?

A

Collagen biosynthesis– hydroxylation of proline

30
Q

What disease occurs as a result of Vitamin C deficiency?

A

Scurvy

31
Q

What is the common name for Vitamin B6?

A

Pyridoxal Phosphate

32
Q

What types of enzymatic reactions is pyridoxal phosphate involved in?

A

Transamination, Deamination, Decarboxylation, Condensation

33
Q

What symptoms can result from B6 deficiency?

A

Microcytic anemia, seizures, neuropathies, dermatitis

34
Q

How does the antibiotic, Isoniazid, work?

A

Competative inhbition of enzymes that use B6

35
Q

What is the only toxic water-soluble vitamin?

A

B6

36
Q

What is the common name for vitamin B1?

A

Thiamine

37
Q

Deficiency of B1 leads to a deficiency in what?

A

ATP

38
Q

How is thiamine deficiency diagnosed?

A

Erythrocyte transketolase activity

39
Q

Deficiency of thiamine can lead to what conditions?

A

BeriBeri, Wernicke-Korsakoff synrome

40
Q

What is the major cause of Wernicke-Korsakoff syndrome?

A

Alcoholism

41
Q

What is the common name of vitamin B3?

A

Niacin

42
Q

Niacin is incorporated into the structure of what teo important molecules?

A

NAD+, NADP+

43
Q

What condition results from niacin deficiency?

A

Pellagra

44
Q

What are the 4 D’s of pellagra?

A

Dermatitis, Diarrhea, Dementia, Death

45
Q

High doses of niacin will inhibit what process?

A

Lipolysis in adipose tissue

46
Q

What is the common name of Vitamin B2?

A

Riboflavin

47
Q

Vitamin B2 is a precursor for which two molecules?

A

FMN, FAD

48
Q

What symptoms can result from a riboflavin deficiency?

A

Dermatitis, cheilosis, glossitis

49
Q

In what type of reactions does biotin serve as a coenzyme?

A

Carboxylation reactions

50
Q

in what three pathways is biotin involved?

A

Pyruvate carboxylase in TCA, Acetyl CoA carboxylase is FA synthesis, Proprionyl-CoA carboxylase in amino acid metabolism

51
Q

What is the common name of Vitamin B5?

A

Pantothenic Acid

52
Q

Which molecules incorporate pantothenic acid into their structure?

A

Acyl carrier protein and coenzyme A

53
Q

What is the most common vitamin deficiency worldwide?

A

Vitamin A deficiency

54
Q

What is the common name of vitamin A?

A

Retinol

55
Q

Vitamin A regulates gene expression in what processes?

A

Embryonic development, lymphocyte and macrophage production,

56
Q

Of what molecule is vitamin A a structural component?

A

Rhodopsin

57
Q

What are the consequences of Vit A deficiency?

A

Decreased growth rate and bone development; increased mortality from infections; sterility; blindness/night blindness

58
Q

What is the active form of Vitamin A?

A

Retinal, Retinoic acid

59
Q

How is Vit A transported through the blood?

A

retinal binding protein

60
Q

What is the active form of Vitamin D?

A

1,25-dihydroxycholecalciferol (calcitriol)

61
Q

What is the primary role of Vit D?

A

Maintaining plasma Ca2+ concentrations

62
Q

Vitamin D deficiency results in what?

A

Demineralization of bones, softening of bones, weak and brittle bones, renal rickets, chronic renal failure

63
Q

What is the most toxic of all the vitamins?

A

Vitamin D

64
Q

What vitamin’s major role is as a cofactor involved in the carboxylation of clotting factors?

A

Vitamin K

65
Q

What is the primary source of Vitamin K?

A

Intestinal flora

66
Q

Vitamin K deficiency can result in what condition?

A

Hypoprothrombinemia

67
Q

Vitamin E is best known for its ________ properties?

A

Antioxidant

Biochemistry: Block 4 (11 decks)

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