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Biochem review USMLE > vitamins > Flashcards

vitamins Flashcards

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USMLE® Step 1 flashcards
1
Q

functions of vitamin A

A

antioxidant
specialized epithelium
vision

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2
Q

vit A used in the treatment of (2)

A

measles

AML M3

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3
Q

symptoms of vit A deficiency

A

first- night blindness

also corneal ulcerations, dry skin

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4
Q

symptoms of vit A excess (4)

A

increased ICP/pseudotumor
bone/joint pain
hair loss
hepatitis

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5
Q

teratogenic effects of excess vitamin A

A

cleft palate, cardiac abnormalities

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6
Q

vitamin B1

A

thiamine

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7
Q

TPP is a cofactor for (4)

A

pyruvate dehydrogenase complex
a-ketoglutarate dehydrogenase complex
transketolase
branched-chain amino acid dehydrogenase

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8
Q

thiamine deficiency

A

impaired glucose metabolism, results in beriberi and WK

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9
Q

dry beriberi

A

peripheral neuropathy, muscle wasting

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10
Q

wet beriberi

A

high output heart failure

edema

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11
Q

areas of brain damaged in WK

A

MD of thalamus

mammillary bodies

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12
Q

treatment of hypoglycemia in alcoholic patients

A

always give thiamine first, giving glucose without thiamine in a thiamine deficient patient can precipitate wernike’s

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13
Q

vitamin B2

A

riboflavin

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14
Q

reactions that riboflavin is involved in

A

oxidation/reduction

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15
Q

FMN

A

NADH dehydrogenase (complex I)

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16
Q

FAD

A

succinate dehydrogenase (complex II)

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17
Q

riboflavin deficiency

A

cheilosis, corneal vascularization

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18
Q

population that is at increased risk for riboflavin deficiency

A

neonates getting phototherapy (B2 degraded)

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19
Q

vitamin B3

A

niacin

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20
Q

amino acid from which niacin is derived, cofactor

A

tryptophan

B6 cofactor

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21
Q

niacin deficiency

A

pellagra- diarrhea, dermatitis, dementia

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22
Q

2 diseases that can cause niacin deficiency

A

hartnup disease (decreased tryptophan absorption) and carcinoid syndrome (increased tryptophan consumption for serotonin synthesis)

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23
Q

vitamin B5

A

pantothenate

24
Q

B5 is a part of

A

CoA for acyl transfers and FA synthase

25
Q

unique symptom of B5 deficiency

A

adrenal insufficiency (due to decreased FA synthase activity)

26
Q

vitamin B6

A

pyridoxine

27
Q

3 general reactions B6 is needed for

A

amino acid synthesis
heme synthesis
transamination

28
Q

B6 deficiency (3)

A

peripheral neuropathy - dec NTs
sideroblastic anemia - dec heme
convulsions- dec GABA

29
Q

vitamin B7

A

biotin

30
Q

type of reaction that requires biotin

A

carboxylation (adding 1C)

31
Q

biotin deficiency

A

rare, related to raw egg white ingestion (avidin)- dermatitis, alopecia

32
Q

vitamin B9

A

folic acid

33
Q

main use of B9

A

purine/thymine synthesis- 1C transfers

34
Q

folate deficiency (2)

A

megaloblastic anemia
no neuropathy
*most common bit def in USA

35
Q

deficiency in pregnancy

A

neural tube defects

36
Q

b12 is a cofactor for (2)

A
  • homocysteine methyltransferase (homocysteine –> methionine)
  • methylmalonyl-CoA mutase (methylmalonyl-coa –> succinyl-CoA)
37
Q

b12 deficiency symptom classes (2)

A
  • megaloblastic anemia

- peripheral neruopathy

38
Q

why does B12 def cause megaloblastic anemia?

A

decreased homocysteine methyltransferase activity leads to decreased conversion of homocysteine to methionine = decreased THF = decreased dTMP pyrimidines

39
Q

why does B12 deficiency cause peripheral neuropathy?

A

increased methylmalonyl-CoA leads to defects in myelin

40
Q

schilling test

A

determine etiology of B12 deficiency, test B12 in urine (decreased B12 in urine indicates decreased absorption)

41
Q

infection that can cause B12 deficiency

A

diphyllobothrium latum

42
Q

general causes of B12 deficiency (3)

A

malabsorption
lack of IF
terminal ileum disease

43
Q

what is SAM?

A

product of methionine + ATP

44
Q

what is the role of SAM?

A

transfers methyl units

45
Q

what reaction is dependent on SAM?

A

conversion of norepinephrine to epinephrine

46
Q

role of vitamin C in collagen synthesis

A

cofactor for the hydroxylation of lysine and proline residues

47
Q

excess vitamin C increases the risk of toxicity from what metal? why?

A

iron toxicity, because it C puts iron in 2+ state making it more readily absorbed

48
Q

sites of hydroxylation for vitamin D

A

liver 25-OH

kidney- 1-OH

49
Q

why is hypercalcemia seen in sarcoidosis?

A

activated macrophages in granulomas increase vitamin D activation

50
Q

another name for vitamin E

A

a-tocopherol

51
Q

main role of vit E

A

antioxidant

52
Q

vit E deficiency

A

hemolysis and posterior column/spinocerebellar tract degeneration (mimics B12 but low MCV)

53
Q

role of vit K

A

catalyzes gamma carboxylation of clotting factors 2, 7, 9, 10, proteins C and S

54
Q

patients at risk for it K deficiency

A

neonates (no flora)

long term abx (depleted flora)

55
Q

what can decrease vit K in breast milk

A

antibiotics taken by mother, especially cephalosporins

56
Q

symptoms of zinc deficiency (4)

A

rash around face, mouth
delayed wound healing
abnormal sense of smell
infertility in males

Biochem review USMLE (11 decks)

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