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USMLE > Biochemistry > Flashcards

Biochemistry Flashcards

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USMLE® Step 1 flashcards
1
Q

6-MP and name its prodrug

A

azathioprine, inhibits prpp to imp

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2
Q

Purines names

A

adenine, guanine

(PURE AS GOLD)

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3
Q

leflunomide

A

inhibits dihydroorate dehydrogenase
(carbamoyl phosph to orotic acid)

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4
Q

pyrimidines

A

(CUT PYRamid)

Cytosine, thymine, uracil

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5
Q

5-fu

A

inhibit thymidylate synthase
(dUMP to dTMP)

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6
Q

drugs that inhibit dhf reductase

A

methotrexate, trimethroprim, pyrimethamine

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7
Q

mycophenolate, ribavirin

A

inhibit dihydrofolate reductase
(imp to gmp)

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8
Q

helicase def in which ds

A

bloom synd (blm deficiency)

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9
Q

irinotecan, topotecan inhibit

A

topoisomerase 1

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10
Q

etoposide, teniposide inhibit

A

topoisomerase 2

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11
Q

fluoroquinolones inhibit

A

top 2 and 4

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12
Q

dna polym 3 has what activity

A

3 to 5 exonuclease

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13
Q

dna polym 1 has which act

A

5 to 3 exonuclease

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14
Q

telomerase adds which sequence

A

ttaggg (Telomerase TAGs for Greatness and Glory)

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15
Q

dna ligase functn

A

links okazaki fragments

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16
Q

lesch-nyan synd

A

deficiency of hgprt

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17
Q

ada def leads to

A

scid

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18
Q

non homologous dna repair dysfunctnl in which ds

A

ataxia telangi-ectasia

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19
Q

nucleotide excision repair occurs in which phase of cell cycle

A

g1

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20
Q

defective nucleotide excision repair in which ds

A

xeroderma pigmentosum

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21
Q

defective mismatch repair in which ds

A

lynch synd (hereditary nonpolyposis colorectal cancer)

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22
Q

homologous dna repair defective in which ds

A

breast cancer brca1 and brca2, also fanconi anemia

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23
Q

missense mutatn ex

A

sickle cell ds

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24
Q

frameshift mutatn ex

A

muscular dystrophy, tay-sachs ds, cystic fibrosis

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25
Q

product os rnap 1,2,3 in eukaryotes

A

rnap1- rRNA, rnap2- mRNA, snRNA, miRNA, rnap3- 5sRNA, tRNA

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26
Q

rnap in prokaryotes

A

only 1 that makes all types of RNA

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27
Q

Amanita phalloides (mushroom) poisoning

A

contains alpha-amanitin which inhibits rnap2, causes dysentry and hepatotoxicity

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28
Q

dactinomycin

A

inhibits rnap in both eukary and prokaryotes

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29
Q

rifampicins (rifabutin and rifampin)

A

inhibit DNA dependent RNA polymerase in prokaryotes

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30
Q

alteration in snRNP assembly

A

causes spinal muscular atrophy due to decreased SMN (survivalmotor neuron protein), leads to hypotonia or floppy baby syndrome

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31
Q

Anti-U1 snRNP antibodies seen in

A

SLE

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32
Q

start codon

A

AUG

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33
Q

stop codons

A

UGA, UAA, UAG

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34
Q

eukaryotic initiation factors (eif) functns

A
  1. identify 5’ cap
  2. assemble 40s + 60s ribosomes
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35
Q

which toxins target ef-2

A

diptheria, pseudomonas

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36
Q

trimming

A

removal of N or C terminal propeptides to convert it into mature protein
eg. trypsinogen to trypsin

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37
Q

chaperone protein

A

maintaing the folding of proteins that is reqd for it for proper functning

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38
Q

cell cycle phases

A

interphase and m phase

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39
Q

interphase consists of

A

g1, g0, s, g2

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40
Q

m phase consists of

A

cytokinesis and mitosis

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41
Q

p53 mechanism

A

p53 activates p21 that further inhibits release of phosphate group from cyclin-cdk complex
(the phospshate displaces ef-2 from RB-Ef2 combinatn
The EF-2 causes gene transcription and the cell continues in the cell cycle from S phase)
all this is prevented by activation of p53

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42
Q

cells that permanently stay in g0 phase

A

neurons, cardiac muscles, skeletal muscles, rbcs

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43
Q

cells most affected by chemotherapy (never enter g0)

A

bone marrow, gut epithelium, skin, hair follicles, germ cells

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44
Q

RER site of synth of

A
  1. proteins
  2. n-linked oligosaccharides
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45
Q

cells rich in rer

A

1.mucus secreting goblet cells of SI
2. antibody secreting plasma cells

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46
Q

RER in neurons called

A

nissl bodies (synthesize neurotransmitter)

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47
Q

SER synthesizes

A
  1. steroids
  2. detoxificatn of drugs, poisons
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48
Q

glucose-6-phosphate locatn

A

SER

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49
Q

Cells rich in SER

A
  1. Hepatocytes
  2. Adrenal Cortex
  3. Gonads
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50
Q

peroxisome functns

A
  1. beta oxidatn of very long chain fa
  2. alpha oxidatn of branched chain fa
  3. catabolism of amino acids and ethanol
  4. synth of bile acids and plasmalogens
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51
Q

what are plasmalogens

A

membrane phospholipids of white matter of brain

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52
Q

zellweger synd

A

AR disorder
Peroxisome dysgenesis due to PEX gene mutatn
hypotonia, seizures, hepatomegaly, death

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53
Q

refsum synd

A

ar disorder
ds of alpha oxidatn
buildup of branched chain fa (phytanic acid)
vision loss (retinitis pigmentosa), hearing loss, ataxia, peripheral neuropathy
rx- low bcfa diet, plasmapharesis

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54
Q

Adreno-leuko-pathy

A

x linked rec ds
ds of beta oxidatn
mutatn of ABCD1 gene
vlcfa build up in ADRENAL GLANDS and white (LEUKO) matter of brain
can lead to adrenal gland crisis, progrressive loss of neurological functn, death

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55
Q

proteasome functn

A

degrades proteins tagged with ubiquitin

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56
Q

ubiquitin proteasome sys defected in

A

some parkinsonism pts

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57
Q

golgi functn

A
  1. distributn center for proteins and lipids from ER to vesicles and plama memb
  2. add mannose-6-p to proteins for lysosomal degradatn
58
Q

endosome functn

A

check material entering the cell and send it either to Golgi, sending to lysosomes for destructn or outside the cell (SORTING CENTER)

59
Q

I-cell ds

A

failure of Golgis to add mannose-6-p to proteins for lysosmal degradatn

60
Q

i cell ds defect

A

defect in n-acetylglucosaminyl-1-phosphotransferase

61
Q

i cell ds features

A

coarse facial features
gingival hyperplasia
corneal clouding
increased plasma levels of lysosomal enzymes
often fatal in childhood

62
Q

signal recognition particle defect

A

increased protein in cytosol
(as it transfers protein-ribosome complex from cytosol to RER)

63
Q

Vesicular trafficking proteins names

A

COP1, COP2, Clathrin

64
Q

COP1

A

cis golgi to ER (retrograde)

65
Q

COP2

A

ER to cis golgi (anterograde)

66
Q

Clathrin

A

trans golgi to lysosomes
plasma memb to endosomes

67
Q

cytoskeletal elements

A

network of protein fibers

68
Q

cystoskeletal elements types

A

microfilaments
int filaments
microtubules

69
Q

microfilaments functn and eg

A

muscle contractn, phagocystosis (actin, microvilli)

70
Q

int filaments fuctn and eg

A

maintain cell structure (vimentin, desmin, cytokeratin, neurofilaments)

71
Q

microtubules functn and eg

A

movement, cell division
(flagella, cilia, mitotic spindle, axonal trafficking)

72
Q

microtubule structure

A

alpha and beta-tubulin and bound to 1 gtp each

73
Q

Retrograde and Anterograde transport proteins

A

REaDY? AttacK!

Retrograde- dynein
anterograde- kinesin

74
Q

Retrograde transport used by what viruses and toxins

A

clost tetani toxin, polio virus, rabies virus, HSV

75
Q

drugs that act on microtubules

A

Mictrotubules Get Constructed Very Terribly

M- Mebendazole
G- Griesofulvin
C- Colchicine
V- vinca alkaloids
T- Taxanes

76
Q

cilia structure constituents

A

9 doublets + 2 singlets

77
Q

basal body constituents

A

9 triplets

78
Q

primary ciliary dyskinesia defect

A

dynein arm defect

79
Q

primary ciliary dyskinesia

A

dysfunctnl ciliated epithelium

80
Q

MC type of primary ciliary dyskinesia

A

kartagener synd

81
Q

kartagener synd features

A
  1. situs inversus
  2. recurrent infectns (sinusitis, ear infectns, bronchiectasis)
  3. inc risk of ectopic pregnancy
82
Q

screening test for kartagener synd

A

dec nasal NO

83
Q

sodium pot pump

A

2 strikes? K you’re still in, 3 strikes? NAh, you’re out.

2 K in, 3 Na out

84
Q

drugs inhibiting Na/K pump

A

Oubain
Digoxin
Digitoxin

85
Q

most abundant protein

A

collagen

86
Q

collagen types

A

type 1- skeleton
type 2- cartilage
type 3- arteries
type 4- basement memb
(SCAB)

87
Q

most common type of collagen

A

type 1

88
Q

dec type 1 collagen productn seen in

A

osteogenesis imperfecta type 1

89
Q

type 3 collagen def in

A

vascular type of ehlers-danlos synd

90
Q

type 4 collagen def in

A

alport synd

91
Q

autoAb against type 4 collagen in

A

goodpasture synd

92
Q

collagen made up of

A

1/3 is of glycine + proline + lysine

93
Q

hydroxylatn in synth of collagen req which vit

A

vit c

94
Q

vit c def

A

scurvy

95
Q

problems in triple helix formatn of collagen seen in

A

osteogenesis imperfecta

96
Q

problems with cross linking of collagen seen in

A

menkes ds

97
Q

osteogenesis imperfecta also called

A

brittle bone ds

98
Q

osteogenesis imperfecta gene defects

A

COL1A1, COL1A2

99
Q

osteogenesis imperfecta features

A

Patients can’t BITE-

B- Bones- multiple fractures
I- Eye- Blue sclerae
T- Teeth- dental imperfectns
E- Ears- hearing loss

100
Q

osteogenesis imperfecta rx

A

bisphosphonates

101
Q

ehlers-danlos synd types

A

classical and vascular

102
Q

classical ED synd gene defect

A

mutatn in type 5 collagen
(COL5A1, COL5A2)

103
Q

vascular ED synd gene defect

A

mutatn in type 3 collagen
(COL3A1)

104
Q

ED synd features

A

hypermobile joints
easy bruising

105
Q

menkes ds defect

A

defective menkes protein (ATP7A)

106
Q

menkes ds mech

A

defective collagen cross linking

107
Q

menkes ds features

A

kinky hair growth, hypotonia, inc risk of cerebral aneurysms, growth retardatn

108
Q

elastin

A

strechy proteins

109
Q

elastin made up of

A

NONHYDROXYLATED proline, lysine, glycine

110
Q

elastin broken down by

A

elastase

111
Q

elastase inh by

A

alpha1-antitrypsin

112
Q

alpha1antitrypsin def leads to

A

COPD

113
Q

Marfan synd defects

A

FBN1 gene mutatn
on chromosome 15
defective fibrillin-1

114
Q

marfan synd features

A

hypermobile joints
arachnodactyly
necrosis of aorta
aortic aneurysm (MC cause of death)
mitral valve prolapse

115
Q

homocysteinuria cause

A

cystathione synthase def

116
Q

homocysteinuria presentatn

A

similar to marfan’s synd except

Autosomal recessive
decrease intellect
can lead to thrombosis
lens dislocatn is downward

117
Q

pcr test functn

A

amplify a desired fragment of DNA

118
Q

pcr uses

A

diagnostic tool for HIV

119
Q

pcr steps

A
  1. denaturatn
  2. annealing
  3. elongatn
120
Q

polymerase used in pcr

A

taq polym

121
Q

crispr functn

A

genome editing tool

122
Q

crispr uses

A

remove virulence factors from pathogens
replacing disease causing alleles
target tumor cells

123
Q

southern blot mech

A

dna cleaving
gel electrophoresis
dna on memb
dna probe added which anneals to its complementary sequence
exposed to film

124
Q

southern blot use

A

identify size of dna seq

125
Q

nothern blot uses what

A

rna

126
Q

northern blot use

A

gene expression

127
Q

western blot uses what

A

protein

128
Q

western blot use

A

determine quantity

129
Q

flow cytometry uses

A

assess size, granularity, protein expression of each cell

130
Q

flow cytometry uses

A

examine hemat abn like
leukemia, paroxysmal nocturnal hemoglobinuria, also in immunodef like HIV

131
Q

microarray uses

A

genotyping
cancer mutatn
forensic analysis

132
Q

microarray used to detect

A
  1. SNPs
  2. CNVs
133
Q

ELISA used to

A

detect presence of a specific antigen or antibody

134
Q

ELISA used to screen for

A

HIV

135
Q

Karyotyping used for

A

visualising chromosomes

136
Q

samples used for karyotyping

A

blood, bone marrow, amniotic fluid

137
Q

what is added in karyotyping to halt chromosome divison

A

colchicine is added to halt them at metaphase

138
Q

fluorescence in situ hybridisatn

A

direct visualisatn of chromosomes wrt genes at molecular level

139
Q

fluorescence in situ hyb can detect what features on chromosomes

A

microdeletn
translocatn
duplicatn

140
Q

molecular cloning uses

A

productn of human proteins in bacteria
eg insulin, GH

141
Q
A

USMLE (3 decks)

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