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Biochemistry: Block 4 > Vitamins > Flashcards

Vitamins Flashcards

(67 cards)

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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
How does a vitamin B12 deficiency result in megaloblastic anemia?
No recycling of 5-methyl THF--> THF; inhibition of Met (SAM) synthesis
26
What are the most common causes of cobalamin deficiency?
Autoimmune atrophic gastritis; gastrectomy; age
27
What is the comon name for Vitamin C?
Ascorbic Acid
28
What vitamin serves as a coenzyme in hydroxylation reactions?
Vitamin C
29
What is vitamin C's main role in the body?
Collagen biosynthesis-- hydroxylation of proline
30
What disease occurs as a result of Vitamin C deficiency?
Scurvy
31
What is the common name for Vitamin B6?
Pyridoxal Phosphate
32
What types of enzymatic reactions is pyridoxal phosphate involved in?
Transamination, Deamination, Decarboxylation, Condensation
33
What symptoms can result from B6 deficiency?
Microcytic anemia, seizures, neuropathies, dermatitis
34
How does the antibiotic, Isoniazid, work?
Competative inhbition of enzymes that use B6
35
What is the only toxic water-soluble vitamin?
B6
36
What is the common name for vitamin B1?
Thiamine
37
Deficiency of B1 leads to a deficiency in what?
ATP
38
How is thiamine deficiency diagnosed?
Erythrocyte transketolase activity
39
Deficiency of thiamine can lead to what conditions?
BeriBeri, Wernicke-Korsakoff synrome
40
What is the major cause of Wernicke-Korsakoff syndrome?
Alcoholism
41
What is the common name of vitamin B3?
Niacin
42
Niacin is incorporated into the structure of what teo important molecules?
NAD+, NADP+
43
What condition results from niacin deficiency?
Pellagra
44
What are the 4 D's of pellagra?
Dermatitis, Diarrhea, Dementia, Death
45
High doses of niacin will inhibit what process?
Lipolysis in adipose tissue
46
What is the common name of Vitamin B2?
Riboflavin
47
Vitamin B2 is a precursor for which two molecules?
FMN, FAD
48
What symptoms can result from a riboflavin deficiency?
Dermatitis, cheilosis, glossitis
49
In what type of reactions does biotin serve as a coenzyme?
Carboxylation reactions
50
in what three pathways is biotin involved?
Pyruvate carboxylase in TCA, Acetyl CoA carboxylase is FA synthesis, Proprionyl-CoA carboxylase in amino acid metabolism
51
What is the common name of Vitamin B5?
Pantothenic Acid
52
Which molecules incorporate pantothenic acid into their structure?
Acyl carrier protein and coenzyme A
53
What is the most common vitamin deficiency worldwide?
Vitamin A deficiency
54
What is the common name of vitamin A?
Retinol
55
Vitamin A regulates gene expression in what processes?
Embryonic development, lymphocyte and macrophage production,
56
Of what molecule is vitamin A a structural component?
Rhodopsin
57
What are the consequences of Vit A deficiency?
Decreased growth rate and bone development; increased mortality from infections; sterility; blindness/night blindness
58
What is the active form of Vitamin A?
Retinal, Retinoic acid
59
How is Vit A transported through the blood?
retinal binding protein
60
What is the active form of Vitamin D?
1,25-dihydroxycholecalciferol (calcitriol)
61
What is the primary role of Vit D?
Maintaining plasma Ca2+ concentrations
62
Vitamin D deficiency results in what?
Demineralization of bones, softening of bones, weak and brittle bones, renal rickets, chronic renal failure
63
What is the most toxic of all the vitamins?
Vitamin D
64
What vitamin's major role is as a cofactor involved in the carboxylation of clotting factors?
Vitamin K
65
What is the primary source of Vitamin K?
Intestinal flora
66
Vitamin K deficiency can result in what condition?
Hypoprothrombinemia
67
Vitamin E is best known for its ________ properties?
Antioxidant

Biochemistry: Block 4 (11 decks)

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