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Step 1 Crush 250! - Hans > Biochem > Flashcards

Biochem Flashcards

1
Q

what enzyme is def in Fabry dz?

A

alpha-galactosidase A

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2
Q

what enzyme is def in Krabbe?

A

galactocerebrosidase

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3
Q

what are the clinical symptoms of Krabbe?

A

globoid cells, optic atrophy, developmental delay, peripheral neuropathy

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4
Q

what substrates are accumulated in Krabbe?

A

galactocerebroside, psychosine

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5
Q

what substrates are accumulated in Fabry?

A

ceramide, trihexoside

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6
Q

what enzyme is def in metachromatic leukodystrophy?

A

arylsulfatase A

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7
Q

what are the clinical symptoms of metachromatic leukodystrophy?

A

central and peripheral demyelination with ataxia, dementia

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8
Q

what substrates are accumulated in metachromatic leukodystrophy?

A

cerebroside sulfate

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9
Q

what are the second trimester quad screen values in Down?

A

low alpha fetoprotein
low estriol
high beta hCG
high inhibin A

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10
Q

quad screen values in Edward?

A

all low (low or normal inhibin A)

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11
Q

what is the unique quad screening test for Patau?

A

low PAPP-A

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12
Q

what paths are associated with inc nuchal translucency?

A

Down and Patau

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13
Q

5% of the causes for Down are

A

4%: Robertsonian translocation (2n=46)

1%: mosaicism (no maternal association, post-fertilization mitotic error)

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14
Q

what path is associated with inc sensitivity to vit D (hypercalcemia) and elfin facies?

A

Williams (microdeletion of ch#7)

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15
Q

trinucleotide repeat for friedreich ataxia?

A

GAA

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16
Q

trinucleotide repeat for huntington?

A

CAG

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17
Q

trinucleotide repeat for myotonic dystrophy?

A

CTG

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18
Q

what is the gene involved in myotonic dystrophy?

A

CTG expansion in the DMPK gene which leads to abnormal expression of myotonin protein kinase

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19
Q

what causes Prader Willi?

A

Maternal imprinting and Paternal deletion

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20
Q

what causes AngelMan?

A

Maternal deletion and Paternal imprinting

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21
Q

25% of the cause for Prader Willi is due to

A

Maternal uniparental disomy (Two imprinted maternal genes are inherited, no paternal gene received)

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22
Q

5% of the cause for AngelMan is due to

A

Paternal uniparental disomy (Two imprinted paternal genes are inherited, no maternal gene received)

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23
Q

what vit overdose lead to symptoms of pseudotumor cerebri (inc ICP, hydrocephalus, headache)?

A

vit A

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24
Q

what are symptoms of chronic vit A toxicity?

A

alopecia, dry skin (scaliness), hepatic toxicity and enlargement, arthralgias, pseudotumor cerebri

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25
Q

what are symptoms of acute vit A toxicity?

A

nausea, vomiting, vertigo, blurred vision

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26
Q

what vit def lead to nyctalopia?

A

nyctalopia (night blindness), vit A def

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27
Q

what are symptoms of vit A def?

A

bitot spots on conjunctiva, frequent infection (immunesuppressed), corneal degeneration, xerosis cutis (scaly skin)

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28
Q

what vit def is associated with corneal vascularization and inflammation of lips?

A

vit B2 (riboflavin)

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29
Q

what vit is req for glycogen phosphorylase and decarboxylation rxn?

A

vit B6 (pyridoxine)

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30
Q

vit B6 (pyridoxine) can be used to treat what glycogen storage dz?

A

McArdle

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31
Q

what enzyme is def in Fabry?

A

alpha galactosidase A

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32
Q

what are the clinical symptoms of Fabry dz?

A

peripheral neuropathy of hands/feet, angiokeratomas, cardiovascular/renal dz

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33
Q

3 glucogenic aa?

A

methionine, valine, histidine

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34
Q

amino acids necessary for purine synthesis?

A

GAG (Glycine, Aspartate, Glutamine)

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35
Q

what drug blocks dihydroorotate dehydrogenase?

A

leflunomide

36
Q

two drugs that block IMP (inosine monophosphate dehydrogenase)?

A

mycophenolate, ribavirin

37
Q

clinical applications of ribavirin?

A

HCV, RSV(though palivizumab is preferred in children)

38
Q

2 DOC for Lesch-Nyhan syndrome?

A

allopurinol, febuxostat (both xanthine oxidase inhibitor)

39
Q

what enzyme excises RNA primer with 5’ –> 3’ exonuclease?

40
Q

fluoroquinolones targets

A

prokaryotic enzymes topoisomerase II (DNA gyrase) and topoisomerase IV

41
Q

what enzyme degrades RNA primer?

42
Q

3 drugs that block dihydrofolate reductase?

A

methotrexate, trimethoprim, pyrimethamine

43
Q

what is the precursor of 6-mercaptopurine?

A

azathioprine

44
Q

ribonucleotide reductase is inhibited by

A

hydroxyurea

45
Q

2 pathologies associated with mutations in nonhomologous end joining

A

ataxia telangiectasia, Fanconi anemia

46
Q

major cause of autosomal recessive SCID?

A

adenosine deaminase deficiency

47
Q

explain the pathophysiology of adenosine daminase deficiency?

A

excess ATP and dATP imbalances nucleotide pool via feedback inhibition of ribonucleotide reductase –> prevents DNA synthesis and thus decreases lymphocyte counts

48
Q

what 2 conditions can trigger the inc transcription in Lac operon?

A
  1. low glucose

2. high lactose

49
Q

example of a frameshift mutation?

A

Duchenne muscular dystrophy

50
Q

what is the name of the enzyme that fills the gap in base excision repair?

A

DNA polymerase beta

51
Q

what is the mechanism of the base excision repair?

A

base specific glycosylase removes altered base and creates AP sites (Apurinic/apyrimidinic)

52
Q

during what phase of cell cycle does mismatch repair takes place?

53
Q

what type of dna repair fixes bulky helix distorting lesions?

A

nucleotide excision repair

54
Q

name of the enzyme that makes tRNA?

55
Q

what is the target of alpha amanitin?

56
Q

what blocks RNA polymerase in both prokaryotes and eukaryotes?

A

Actinomycin D

57
Q

which enzyme opens DNA at promoter site?

58
Q

what is the most common form of osteogenesis imperfecta?

A

autosomal dominant with dec production of normal type 1 collagen

59
Q

in OI, what causes the hearing loss?

A

abnormal ossicles

60
Q

describe the tooth abnormalities in OI

A

opalescent teeth that wear easily due to lack of dentin (dentinogenesis imperfecta)

61
Q

OI can be confused with

A

child abuse

62
Q

during the cross linking process of collagen what plays an important role?

A

reinforcement of many staggered tropocollagen molecules by covalent lysine-hydroxylysine cross linkage (by copper containing lysyl oxidase) to make collagen fibrils

63
Q

what are the 2 paths associated with problems in cross linking?

A

Ehlers Danlos, Menkes

64
Q

In Menkes, what protein causes the problem?

A

ATP7A protein leads to dec activity of lysyl oxidase which utilizes copper

65
Q

what nutrition can lead to delayed wound healing, hypogonadism, dysgeusia

66
Q

why is zinc important?

A

important in the formation of zinc fingers which are transcription factor motif

67
Q

what serves as scaffolding with fibrillin?

A

tropoelastin

68
Q

name 3 major amino acids that make up elastin?

A

nonhydroxylated proline, glycine, and lysine

69
Q

what gives elastin its elastic properties?

A

extracellular cross linking

70
Q

what inhibits elastase?

A

alpha 1 antitrypsin

71
Q

causes for wrinkles?

A

due to dec collagen and elastin production

72
Q

urinary cyanide-nitroprusside test came out positive, what is the diagnosis?

A

cystinuria

73
Q

what is the defect in cystinuria?

A

hereditary defect of renal PCT

74
Q

name of the rate determining enzyme in glycolysis?

A

phosphofrucktokinase 1 (PFK-1)

75
Q

rate determining enzyme of gluconeogenesis?

A

fructose 1,6 bisphosphatase

76
Q

rate determining enzyme of TCA cycle?

A

isocitrate dehydrogenase

77
Q

what vitamin def leads to broad collar rash?

A

vit b3, niacin

78
Q

path associated with precocious puberty, multiple endocrine abnormalities, and unilateral cafe au liat spot?

A

McCune Albright syndrome

79
Q

path associated with “polyostotic fibrous dysplasia?”

A

McCune Albright syndrome

80
Q

what is another path associated with “cafe au liat spots?”

A

neurofibromatosis type I (von Recklinghausen dz)

81
Q

what path can mimic pellagra like symptoms? and why?

82
Q

disulfiram blocks what enzyme?

A

acetaldehyde dehydrogenase

83
Q

what drug blocks alcohol dehydrogenase?

A

fomepizole

84
Q

what are the clinical applications for fomepizole?

A

methanol and ethylene glycol antidote

85
Q

apolipoprotein that functions as lipoprotein lipase cofactor?

86
Q

apolipoprotein that functions LCAT (lecithin-cholesterol acyltransferase) activator?

87
Q

what apolipoprotein mediates chylomicron secretion?

Step 1 Crush 250! - Hans (41 decks)

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