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Board Micro > Biochem > Flashcards

Biochem Flashcards

1
Q

Pt presents with self mutilation, mental retardation, dystonia, and gout.
What is elevated in blood stream?
What is mechanism?

FA 64

A

Results in excess uric acid production and de novo purine synthesis.

Defective purine salvage due to absent HGPRT:
converts Hypoxanthine into IMP
converts Guanine into GMP

X-linked recessive. Lesch-Nyhan syndrome

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2
Q

Pt with joint pain and hematuria has rhomboid crystals are in urine as well as hyperuricemia.
How to treat the urine crystals?
How would you treat the pt’s joint pain that they are having and what’s its mechanism?

A

Uric acid precipitates at acidic / low pH. Treatment is alkalinization of urine. (FA 544)

Treat gout with allopurinol which blocks xanthine oxidase to stop hypoxanthine from being converted into uric acid (FA 64)

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3
Q

Child is found to have cherry-red spots on macula as well as progressive neurodegeneration, hepatosplenomegaly, and foam cells.
What is the enzyme deficiency?

A

Classic presentation with Cherry red macula of either Tay-Sachs or Niemann-Pick (FA 624)

Niemann-Pick has hepatosplenomegaly and lipid-laden macrophages.
Enzyme deficiency is sphingomyelinase resulting in accumulation of sphingomyelin.

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4
Q

Cherry-red spot on macula found.

What is differentiation symptom between Niemann-Pick and Tay-Sachs disease?

A

Niemann-Pick has hepatosplenomegaly (sphingomyelinase deficiency) (FA 111)

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5
Q

Pt with developmental delay, gargoylism, and hepatosplenomegaly is found to have abnormal urine sample.
What is in urine sample / is the accumulated substance?
What could be the two diseases?

A

Heparan sulfate and dermatan sulfate. (FA 111)

Hurler syndrome
vs
Hunter syndrome (no corneal clouding)

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6
Q

Child boy with gargoylism, hepatosplenomegaly, and no corneal clouding is found to have elevated heparan sulfate and dermatain sulfate.

Enzyme deficiency? Inheritance?

A

Hunter syndrome: Iduronate sulfatase deficiency.

X-linked recessive. (FA 111)

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7
Q

Draw out diagram of lysosomal storage diseases

at top: GM2

A

FA 111

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8
Q

Classical symptoms of Gaucher disease.

Enzyme deficiency?

A 
FA 111, 625
10 y/o pt with:
Hepatosplenomegaly
Pancytopenia (anemia, leukocytopenia)
osteoporosis 
aseptic necrosis of femur ('flask' looking)
Bone section taken and histo slide is shown: Shows crumpled tissue paper macrophages
Enz: Glucocerebrosidase
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9
Q

Findings of Fabry

Enzyme deficiency

A 
Peripheral neuropathy of hands/feet
angiokeratomas
cardiovascular/renal disease 
alpha - galactosidase A
FA 111
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10
Q

10 y/o pt with angiokeratomas, peripheral neuropathy of hands and feet, and heart problems.
What enzyme deficiency?
Accumulated substrate?

A

alpha galactosidase A
ceramide trihexosidase
FA 111

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11
Q

Classic presentation of Niemann-Pick disease

enzyme deficiency

A 
sphingomyelinase deficiency
child pt with hepatosplenomegaly
foam cells (lipid-laden macrophages)
cherry red spot on macula
FA 111, 626
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12
Q

Hereditary nonpolyposis colorectal cancer
enzyme deficiency
what part of cell cycle

A

defective mis match repair enzymes
G2
FA 67, p 113

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13
Q

Colorectal cancer arises de novo (not from adenomatous polyp), young age, and on right side

A

defective mismatch repair enzyme, G2
hereditary nonpolyposis colorectal cancer
FA 67, p113

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14
Q

Rifampin

A

inhibits prokaryotic RNA polymerase

FA 68

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15
Q

Amanita phalloides

A

death cap mushroom
alpha amanitin toxin which inhibits RNA polymerase II
hepatotoxicity
FA 68

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16
Q

Actinomycin D

A

inhibits RNA polymerase in both prokaryotes and eukaryotes
chemotherapeutic
FA 68

17
Q

Pt with butterfly rash, endocarditis, fever, arthritis.

antibody testing is done. what are these antibodies specific against and what is its role?

A

anti smith antibodies are specific against spliceosomal snRNP’s.
these remove introns as Lariat-shaped bodies
FA 69

18
Q

What is on the 3’ end of tRNA? (aminoacyl end)

what direction is the anticodon?

A

CCA on 3’ end, and amino acid is added here by aninoacyl-tRNA synthetase. 5’-CCA-3’
anticodon is 3’-5’ match to the 5’-3’ codon
FA 70

19
Q

mRNA start codon

what does it code for

A

AUG
codes for methionine in eurkaryotes
codes for fMet (N formylmethionine) in prokaryotes)

20
Q

mRNA stop codons

A 
UGA, UAA, UAG
U Go away
U are away 
U are gone 
FA 67
21
Q

mRNA start codon for prokaryotes

what is special about it

A

AUG codes for fMet
this is a neutrophil chemotaxic agent
FA 67

22
Q

genetic difference between duchenne’s and becker’s muscular dystrophy

A

duchenne is frameshift insertion mutation of dystrophin gene
becker’s is non-frameshit insertion
fA 85

23
Q

Child pt has calf psuedohypertrophy and has gower’s sign

Inheritance?

A

Frameshift mutation (not divisible by 3)
X-linked recessive
Duchenne’s Muscular Dystrophy, mutation of dystrophin gene
FA 624, 85, 66

24
Q

Shigella and enterohemorrhagic E. coli (EHEC) release what toxins?
what is mechanism of these toxins?

A

Shiga toxin and shiga-like toxin
inactivate 60S ribosome by removing adenine from rRNA
FA 124,

25
Q

symptoms of shigella? Toxin? What is the mechanism?

A

GI mucosal damage -> dysenterry
enhances cytokine release, causing hemolytic uremic syndrome (HUS)
Findings:
schistocytosis, renal insufficiency (thrombi), fever,
thrombocytopenia with increased bleeding time, NL PT/PTT, megakaryocytes on BM biopsy

poma 33, FA 124

26
Q

Mechanism of diphtheriae toxin

A

inactivates elongation factor (EF-2) via ADP-ribosylation of EF-2
Ribosome moves peptidyl tRNA to P-site (translocation) during elongation
FA 124, 71

27
Q

Mechansim of exotoxin A

what bacteria releases it?

A

ADP-ribosylation of EF-2
Ribosome moves peptidyl tRNA to P-site (translocation) during elongation
FA 124, 71

28
Q

Neomycin is used for bowel surgery.
what type of bacteria is it used against?
What is the mechanism?

A

gram-negative rods

bctericidal; irreversible inhibition of initiation complex thru binding of 30s subunit

29
Q

child presents with coarse facial features, clouded corneas, and restricted joint movement.
Suspect Hurler’s, but urine does not show ________ or ______ and blood result is high in lysosomal enzymes
enzyme defect? mechansim?

A

Hurler: heparan sulfate, dermatan sulfate in urine

Enz: N-acetylclugosaminyl-1-phosphotransferase
Golgi cannot phosphorylate mannose residues (decreased mannose-6-phosphate) on glycoproteins
FA 73, FA 111

30
Q

High glycine content in fibroblasts suggests synthesis of what?

A

collagen; Gly-X-Y
wound repair
fa 76

31
Q

Swollen gums, mucosal bleeding, poor wound healing, petechiae

A

Scurvy
vitamin C deficiency; cannot hydroxylate proline/lysine for collagen synth
FA 628, 76, 93

32
Q

Blue scera, multiple fractures in child

what organelle

A 
osteogenesis imperfect (AD) 
defect in collagen I synthesis 
glycosylation in rough endoplasmic reticulum 
FA 624, 76, 75
33
Q

Ehlers danlos
Clinical presentation
deficiency in what

A

elastic skin, hypermobility of joints, increased bleeding tendency
collagen type V deficiency (III in vascular type)
FA 625, 77

34
Q

elastic skin, hypermobility of joints
what heart defect?
could lead to what vascular emergency?

A

Mitral valve prolapse (MVP)
Ehlers-Danlos (defective collagen synthesis / cross-linking, AD or AR)
berry and aortic aneurysm
FA 77, 625

35
Q

kinky hair, growth retardation, hypotonia
what gene protein defect?
mechanism?

A

Marfan, XLR
ATP7A - can’t absorb Cu2+, necessary for lysyl oxidase and cross-linkage of collagen
FA 77

36
Q

Type IV collagen
where is it found?
What diseases?

A

Basement membrane, basal lamina, Lens.
Alport syndrome (XLR mutation) FA 541
Goodpasture’s (autoantibody, leading to what? FA 541)
FA 75

37
Q

Hereditary nephritis, sensorineural hearing loss, cataracts

A 
Alport syndrome (collagen IV mutation) 
FA 626, 75, 541

“can’t seen can’t pee, can’t hear a buzzing bee”

38
Q

Adrenoleukodystrophy

A

XLR. Disrupted metabolism of very-long chain fatty acids -> build up in nervous system, adrenal gland, testes
long term coma/death and adrenal gland crisis
FA 489

Board Micro (10 decks)

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