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USMLE First Aid > Biochemistry > Flashcards

Biochemistry Flashcards

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USMLE® Step 1 flashcards
1
Q

2 major histone modifications

A

Acetylation: relaxes DNA coiling
Methylation: increases DNA coiling

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2
Q

Which base has a methyl group?

A

Thymine

THYmine has meTHYl

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3
Q

Which base de-aminates to uracil?

A

Cytosine

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4
Q

3 amino acids necessary for purine synthesis?

A

Glycine
Aspartate
Glutamine
(GAG)

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5
Q

2 Purine Salvage Deficiencies

A

Adenosine Deaminase Deficiency (SCID)
Lesch-Nyhan Syndrome (loss of HGPRT)
- Hyperuricemia, gout, pissed off, retardation, dysTonia

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6
Q

Nucleotide Excision Repair

A

Endonuclease –> polymerase/ligase
Removes bulky lesions (ex thymine dimers)
G1 phase only
Defective in Xeroderma Pigmentosum (can’t fix pyrimidine dimers)

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7
Q

Base Excision Repair

A

Glycosylase creates AP site –> endonuclease (5’) & Lyase (3’) –> polymerase beta & ligase
Throughout cell cycle
Important for spontaneous or toxic deamination

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8
Q

Mismatch Repair

A

Mostly in G2 phase

Defective in hereditary nonpolyposis colorectal cancer

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9
Q

Start codon

A

AUG (Methionine)

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10
Q

Stop Codons

A

UGA, UAG, UAA

U Go Away, U Are Away, U Are Gone

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11
Q

4 Types of DNA mutations

A

Silent (same AA)
Missense (different AA)
Nonsense (early stop)
Frameshift

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12
Q

Lac Operon

A

Genetic response to environmental change, ex w/o glucose, increased AC activity and abundant lactose causes gene expression changes

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13
Q

DNA is synthesized in the ___ direction

A

5’ to 3’ w/ 3’ hydroxyl attacking 5’ phosphate

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14
Q

mRNA is read in the __ direction

A

5’ to 3’

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15
Q

Eukaryotic RNA polymerases

A

RNA polymerase I (rRNA)
RNA polymerase II (mRNA)
RNA polymerase III (tRNA)

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16
Q

RNA polymerase inhibitors

A

alpha-amanitin (death cap): RNA polymerase II
Rifampin: prokaryotic RNA polymerase inhibitor
Actinomycin D: generic RNA polymerase inhibitor

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17
Q

Alpha-Amanitin

A

RNA polymerase II inhibitor, causes severe hepatotoxicity

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18
Q

Rifampin

A

Prokaryotic RNA polymerase inhibitor

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19
Q

Actinomycin D

A

generic RNA polymerase inhibitor, Euks and Pros

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20
Q

Prokaryotic RNA polymerases

A

Single RNA polymerase

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21
Q

mRNA processing steps

A

5’ Cap (7-methylguanosine)
splicing of introns
3’ polyadenylation

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22
Q

2 major amino acids in histones

A

lysine

arginine

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23
Q

Which bases get methylated for repression?

A

cytosine and adenine

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24
Q

Which base synthesis is more complicated? Purine or Pyrimidine? Which uses an intermediary base? Where do most drugs act?

A

Pyrimidine is more complicated and involves orotic acid intermediary. Most drugs act on pyrimidine synthesis.

25
Q

Adenosine Deaminase Deficiency

A

too much ATP and dATP imbalances the nucleotide pool and prevents DNA synthesis
This generally causes SCID

26
Q

Lesch-Nyhan Syndrome

A

Defective purine salvage from lack of HGPRT (creates IMP and GMP)
Symptoms: Hyperuricemia, Gout, Aggression (pissed off), Retardation, and DysTonia

27
Q

Nonhomologous End Joining

A

No need for homology. Some DNA might be lost.

Mutated in Ataxia telangiectasia and Fanconi Anemia

28
Q

Splicing

A

mediated by snRNPs, form lariat that is cut out
Anti-sliceosome ABs highly specific for SLE
Anti-U1 ABs associated with mixed connective tissue disease

29
Q

Anti-Spliceosome Antibodies

A

Associated with SLE

30
Q

Anti-U1 Antibodies

A

Associated with mixed connective tissue disease

31
Q

4 arms of a tRNA

A

Acceptor stem (3’ CCA sequence)
T-arm (binds ribosome)
D-arm (associates w/ tRNA synthetase)
Anti-codon loop

32
Q

Energy source for tRNA charging (adding amino acid)

A

ATP

33
Q

Energy source for protein synthesis initiation

A

GTP

34
Q

Cell cycle regulated by 3 major types of proteins

A

Cyclins, Cyclin-dependent kinases, and tumor suppressors

35
Q

Which cell cycle regulator is constitutively expressed?

A

Cyclin-dependent kinases

36
Q

Which amino acids are N-glycosylated?

A

asparagine

37
Q

Which amino acids are O-glycosylated?

A

serine and threonine

38
Q

What is added in Golgi to traffic proteins to lysosomes?

A

Mannose-6-phosphate

This process is defective in I-cell disease

39
Q

Types of vesicular trafficking proteins

A

COPI (Golgi to ER, retrograde)
COPII (ER to Golgi, anterograde)
Clathrin (Golgi to other locations)

40
Q

3 types of filaments

A

Mcirofilaments (ex actin)
Intermediate Filaments (ex vimentin, desmin)
Microtubules (ex cilia, flagella)

41
Q

Vimentin stains positive in…..

A

Connective Tissue

42
Q

Desmin stains positive in…..

A

Muscle

43
Q

Cytokeratin stains positive in…..

A

Epithelial Cells

44
Q

GFAP stains positive in…..

A

Neuroglia

45
Q

Neurofilaments stain positive in…..

A

Neurons

46
Q

2 Molecular Motor proteins for microtubules

A

Dynein and Kinesin

47
Q

Which motor protein moves retrograde

A

Dynein

48
Q

Which motor protein moves anterograde?

A

Kinesin

49
Q

Pneumonic for drugs that act on microtubules

A

Microtubules Get Constructed Very Poorly

Mebendazole, Griseofulvin, Colchicine, Vincristine/Vinblastine, Paclitaxel

50
Q

Disease with immotile cilia from dynein defect

A

Kartagener syndrome

51
Q

Symptoms of Kartagener syndrome

A

infertility (males and females), increased ectopic pregnancy risk, bronchiectasis, recurrent sinusitis, and situs inversus

52
Q

Types of Collagen and uses in body

A 
Type I: Bone, Skin, Tendons
Type II: Cartilage
Type III: Reticulin (blood vessels)
Type IV: Basement Membrane
Be (So Totally) Cool, Read Books
53
Q

3 main amino acids that make up collagen

A

Glycine, Lysine, Proline

54
Q

Hydroxylation of Collagen

A

Occurs in RER, requires vitamin C (scurvy)

55
Q

Osteogenesis Imperfecta

A

AD, reduced type I collagen synthesis

Broken bones, blue sclerae, hearing loss, dental issues

56
Q

Ehlers Danlos Syndrome

A

AD or AR, poor collagen synthesis

  • Type V mutation is classic
  • Type III mutation is less common vascular form
57
Q

Menkes disease

A

XR, impaired copper absorption, causes low lysyl oxidase activity
symptoms: kinky hair, growth retardation, hypotonia

58
Q

Marfan Syndrome

A

defect in fibrillin (forms elastin sheath)

59
Q

Blotting Techniques

A

SNoW DRoP
Southern=DNA
Northern=RNA
Western=Protein

USMLE First Aid (4 decks)

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