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USMLE Organ Systems > BioChem > Flashcards

BioChem Flashcards

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USMLE® Step 1 flashcards
0
Q

Microtubules are used for what main function (and 5 subcategories)?

A

Movement

[cilia, flagella, mitotic spindle, axonal trafficking, centrioles]

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1
Q

Actin/Myosin are used for what 4 things?

A

muscle contraction, microvilli, cytokinesis, adherens junction

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2
Q

Intermediate filaments are used for what main function?

A

Structure

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4
Q

Intermediate filaments have what 5 types? Each is located where?

A
  • Vimentin - connective tissue
  • DesMin - Muscle
  • Cytokeratin - epithelial cells
  • Gfap- NeuroGlia
  • Neurofilaments - Neurons
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5
Q

Type 1 collagen: What 7 functions?

A

bone, skin, tendon,

dentin, fascia, cornea, late wound repair

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6
Q

Type 2 collagen: what 3 uses?

A

cartilage,

vitreous body, nucleus pulposus

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7
Q

Type 3 collagen: what 5 uses?

A

Reticulin

[BLOOD VESSELS, skin, uterus, fetal tissue, granulation tissue]

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8
Q

Type 4 collagen: what 3 uses?

A

basement membrane,

basal lamina, lens

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9
Q

ADPKD: chromosome & char?

A

PKD1 (85%)=16, PKD2=4.

  • Always bilateral enlargement due to large cysts
  • Think of “cysts in kidney, liver, and brain (aneurysms) plus mitral prolapse”
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10
Q

Fam Aden Polyposis: chromosome & char?

A
  • 5
  • Colon covered in polyps post-puberty. -> Cancer.
  • Also other GI, thyroid, CNS tumors
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11
Q

Fam Hypercholesterolemia: char?

A
  • Defective or absent LDL receptor

- Xanthomas/athero, esp achilles

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12
Q

Hereditary hemorrhagic telangiectasia: char?

A
  • think of complications of vessels. A.k.a. Osler-Weber-Rendu
  • Telangiectasia
  • RECURRENT epistaxis
  • Lip splotches
  • skin discoloration, arteriovenous malformations, GI bleed, hematuria
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13
Q

Hereditary spherocytosis: char?

A

1) ankyrin 2)spectrin. Up MCHC (heme conc.)

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14
Q

Huntington: chromosome & char?

A
  • Hunting 4 food
  • Depressed, crazy, & dancing (chorea) in a CAGe w/ caudate atrophy & down GABA, ACh
  • Hypermethylation of histones -> Gene silencing
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15
Q

Marfan: chromosome & char?

A
  • Fibrillin-1

- Cystic medial necrosis of aorta->dissection, floppy mitral. Sublux of lens up and temporally. Other classic things.

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16
Q

Tuberous sclerosis: char? (yes all are important to memorize)

A
  • benign hamartomas (neurocutaneous & ANY organ system)
  • Renal angiomyolipomas
  • Ash leaf spots
  • rhabdomyoma
  • adenoma sebaceum in nasolabial folds (acne-like papules)
  • seizures
  • incomplete penetrance AND variable expression
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17
Q

von Hippel-Lindau

A
  • 3p (3 words) VHL gene (tumor suppressor deletion) auto dominant
  • Abnormal vessel growth -> Tumors everywhere benign/malignant!
  • Hemangioblastomas in CNS
  • Bilateral renal cell carcinoma (“3p is for peeing”)
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18
Q

Achondroplasia: gene and char?

A
  • FGFR3
  • Normal trunk, tiny limbs, bulging forehead.
  • Due to advanced paternal age! 70% are spontaneous mutations.
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19
Q

i cell dz: defect? clinical presentation?

A
  • Golgi phosphotransferase (phosphorylates mannose residues to send to lysosome)
  • Coarse facial features, clouded cornease, restricted joint movement, high plasma lysosomal enzymes
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20
Q

Drugs that act on microtubules?

A

“microtubules get constructed very poorly”

  • mebendazole (helminth)
  • griseofulvin (fungal)
  • colchicine (gout)
  • vincristine/vinblastine (cancer)
  • paclitaxel (cancer- uniquely, prevents DEpolymerization)
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21
Q

Collagen synthesis steps?

A
  1. Make Gly - X - Y (often X and Y are proline, lysine)
  2. Hydroxylate (vit C)
  3. Glycosylate hydroxylysine then PROCOLLAGEN H and disulfide bonds form (triple helix, prob=osteogenesis imperfecta)
  4. Exocytosis
  5. Cleave disulfide terminal regions ->insoluble tropocollagen
  6. Covalent-link tropocollagens (staggered) at lysine-hydroxylysine by Cu-containing (Menke’s Dz=Cu deficiency) lysyl oxidase ->collagen. (prob crosslinking= Ehlers Danlos)

[recall Zn is needed to break down collagen (wound healing]

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22
Q

Osteogenesis Imperfecta clinical presentation?

A

“Osteogenesis Imperfecta degrades you FAST”

  • Fractures
  • Auditory ossicles (hearing loss)
  • Sclera (BLUE!!)
  • Teeth (lack dentin)
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23
Q

Which connective tissue component is NOT hydroxylated at proline?

A

Elastin

[recall alpha 1 antitrypsin inhibits elastase]

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24
Q

What a.a.’s are needed to make purines?

A

“Need these to GED (get) purines” (using their 1-letter codes)
G (glycine)
E (glutamate)
D (aspartic acid)

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25
Q

What drug is used for choreocarcinoma?

A

methotrexate

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26
Q

What 3 drugs affect DNA topoisomerase?

A

fluoroquinolones, irinotecan, topotecan

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27
Q

What amino acids aren’t “redundant” in their code?

A

methionine (AUG), tryptophan (UGG)

28
Q

DNA Pol 3 (prokaryotic) has what kind of exonuclease? Howa about DNA Pol 1?

A
  • 3 to 5 (to proofread)

- 5 to 3 (to excise RNA primer)

29
Q

Nuceotide Excision Repair is for?

A
  • “NER repair= bulky XER disease”
  • ENDONUCLEASE activity

[nucleotide excision repair is for bulky (pyrimidine dimers due to UV) repair. A defect gives xeroderma pigmentosum. (premature skin agin, multiple melanomas, sunburn, dry cracking skin)]

30
Q

Base excision repair is for?

A
  • “Bring cartoons to BASE when they’ve been spontaneously DE-ANIMATED”
  • GLYCOSYLASE activity, followed by the normal NER steps.
31
Q

Mismatch repair is for?

A
  • Newly synthesized DNA repair

- “Giving MISMATCHED RECTUMS (HNPCC) to the wrong patient would be disastrous!”

32
Q

Nonhomologous end joining is mutated in what diseases?

A

ataxia telangiectasia, BRCA, FANCD2, CHK2

33
Q

What would be the Spontaneous Deamination of the following nucleotides? C, adenine, G

A

C-> U
Adenine ->hypoxanthine
G -> Xanthine

34
Q

What is the DNA replication termination signal?

A

AATAAA

“ata’ boy, you’re all done!”

35
Q

An intron begins with what? Ends with what?

A
  • GU “GT started” (DNA strand will be a GT not GU)

- AG “AG done” (All done, like a child is saying it)

36
Q

Anti-U1 RNP antibodies indicate what dz?

A

Mixed connective tissue disease

37
Q

Anti-Smith antibodies (lupus) attack what?

A

snRNP’s (normally help splice pre-mRNA)

38
Q

Polyadenylation signal?

A

AAUAAA (notice similarity to DNA replication termination signal: AATAAA)

39
Q

Rb (tumor suppressor) is on what chromosome?

A

13 (think cancer and 13! scary!)

40
Q

ouabain: mechanism?

A

binds K site of Na/K pump

41
Q

digoxin: mechanism?

A

inhibits ATPase of Na/K pump

42
Q

Auto Recessive diseases? (minus the ones that are obvious)

A
  • albinism
  • glycogen storage diseases
  • hemochromatosis
  • Kartagener
  • All lysosomal storage dz except Fabry and Hunter
  • PKU
  • thalassemias
  • Wilson dz
43
Q

X-linked recessive disorders?

A

“Friendly BOG SCOWLD: SHH !!”

  • Fabry
  • Bruton
  • Ocular albinism
  • G6PD
  • Sideroblastic anemia due to mutation in rate-limiting Delta-ALA synthase
  • Chronic Granulomatous dz
  • Ornithine transcarbamylase deficiency
  • Wiskott-Aldrich
  • Lesch-Nyhan
  • Duchenne (and Becker)
  • SCID
  • Hemophilia A & B
  • Hunter syndrome
44
Q

fomepizole function?

A

inhibits alcohol dehydrogenase (1st step). Antidote for methanol or ethylene glycol poisoning, NOT isopropyl)

45
Q

Disulfiram function?

A

inhibit acetaldehyde dehydrogenase

46
Q

Which metabolisms occur in mitochondria?

A

FA oxidation, acetyl-CoA production, TCA cycle, ox phos

47
Q

Which metabolisms occur in cytoplasm?

A

glycolysis, FA synth, HMP shunt, protein synth (RER), steroid synth (SER) & cholesterol synth

48
Q

Which metabolisms occur in both places?

A

HUGs take two.

Heme synth, urea cycle, gluconeogenesis

49
Q

Arsenic function?

A

glycolysis produces zero net ATP

50
Q

What is carried by CoA & lipoamide?

A

acyl groups R-C=O

51
Q

What is carried by biotin?

A

CO2

52
Q

What is carried by THF?

A

1-carbon units

53
Q

What is carried by SAM?

A

CH3 groups

54
Q

What is carried by TPP?

A

aldehydes

55
Q

Arginine can be made into?

A

creatine
urea
nitric oxide (req BH4)

56
Q

Glutamate can be made into?

A

GABA (req B6)

Glutathione

57
Q

Glycine can be made into?

A

porphyrin (req B6) -> Heme

58
Q

Histidine can be made into?

A

histamine (req B6)

59
Q

Tryptophan can be made into?

A

Niacin (req B6) ->NAD+

Serotonin (req B6 & BH4) -> melatonin

60
Q

Phe requires what cofactor to make tyrosine?

A

BH4

61
Q

Tyrosine requires what cofactor to make dopa?

A

B6

[tyrosine can also make thyroxine or homogentisic acid]

62
Q

Dopa requires what cofactor to make dopamine?

A

B6

[Dopa can also make melanin]

63
Q

Dopamine requires what cofactor to make NE?

A

Vit C

64
Q

NE requires what cofactor to make Epi?

A

SAM

[Cortisol stimulates this conversion!]

65
Q

metanephrine & normetanephrine are made into?

A

VMA (vanillymandelic acid)

66
Q

What is made into homovanillic acid (HMA)?

A

dopamine

USMLE Organ Systems (10 decks)

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