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USMLE Studying > Biochemistry Info > Flashcards

Biochemistry Info Flashcards

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USMLE® Step 1 flashcards
1
Q

What AA do you need to make Purines?

A

Glycine

Aspartate

Glutamine

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2
Q

Difference between Nucleotide and Nucleoside?

A

Side = base + (deoxy)ribose (SUGAR)

Tide = base + (deoxy)ribose + PhophaTe

linked by 3’-5’ Phosphodiester bone

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3
Q

What are the 2 processes that Carbamoyl Phosphate is involved in?

A

1) De Novo Pyrimidine Synthesis - Glutamine to carbamoyl phosph to orotic acid
2) Urea Cycle

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4
Q

What does Leflunomide do?

A

inhibits dihydrooorotate dehydrogenase from taking Carbamoyl phosphate + Asparatate to Orotic Acid in de novo Pyr synth

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5
Q

What does Mycophenolate and Ribavirin inhibit?

A

IMP dehydrogenase making IMP to GMP

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6
Q

What does Hydroxyurea inhibit?

A

RIBONUCLEOTIDE REDUCTASE

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7
Q

What does 6MP and Azathioprine inhibit?

A

de novo Purine Synthesis from PRPP

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8
Q

What does 5FU inhibit?

A

Thymidylate Synthase - decreased dTMP

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9
Q

What is Lesch-Nyan Syndrome?

A

defective purine salvage bc absent HGPRT which converts Hypoxanthine to IMP and Guanine to GMP

Increased Uric Acid production and de novo purine synthesis - XLRecessive

Hyperuricemia

Gout

Pissed off - self mutilation and aggression

Retardation

dysTonia

Tx allopurinol and Feboxostat

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10
Q

What are the AA encoded by only 1 codon?

A

AUG - Methionine

UGG - Tryptophan

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11
Q

How do Floroquinolones work in DNA replication?

A

Antibiotics that inhibit prokaryotic enzyme topoisomerases 2 (DNA gyrase) and Topoisom IV which normally create single and double strand breaks in DNA to add or remove supercoils

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12
Q

What is DNA polymerase 3 and significance of it?

A

PROKARYOTIC ONLY

elongates leadding by adding to 3’ end

elongates laggin until reaches preceeding fragment

5’–> 3’ Synthesis

Proofreads 3’–> 5’ exonuclease

vs DNA pol 1

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13
Q

What is DNA pol 1 and significance?

A

PROKARYOTIC ONLY

Degrades RNA primer and replaces it w/ DNA

same as Pol 3 except also has 5’–> 3’ Exonuclease

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14
Q

What is telomerase?

A

RNA dependent DNA polymerase that adds DNA to 3’ ends of Chromosomes to avoid loss of genetic material w/ duplication

EUKARYOTES ONLY

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15
Q

What are mutations in DNA?

A

Silent < missense < nonsense < Frameshift

Point mutations:

Transition - Pur to Pur or Pyr to Pyr

Transversion - Pur to Pyr or Pyr to Pur

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16
Q

What is a clinical example of a missense mutation? Frameshift mutation?

A

Missense - nuc substitution yields new AA in protein

  • ex. Sicke Cell Disease substitution of Glu w/ Val

Frameshift - deletion or insertion that changes 3 aa frame for codons

ex. Duchenne Muscular Dystrophy

17
Q

When does Nucleotide Excision Repair occur? Disease associated?

A

G1 Phase of Cell cycle

repairs bulky-helix distorting lesions w/ Endonucleoases

Xeroderma Pigmentosum!!!! prevents repair of pyrimidine dimers from UV light bc defective NER

18
Q

When does Mismatch repair occur? Clinical disease w/ deficiency?

A

recognize newly synthesized strand and mismatched removed and resealed

G2 phase of cell cycle

HNPCC!!!!!!

19
Q

What are 2 diseases w/ mutation in Non-homologous end joining?

A

Ataxia Telangiectasia

Fanconi Aneima

20
Q

What direction is RNA/DNA and Protein synthesis made in?

A

DNA and RNA made in 5’ –> 3’ and 5’ end has Triphosphtae for energy

Protein Syntesis is N to C

mRNA to protein is read 5 to 3

21
Q

Eukaryotic RNA polymerases - what are they and what do they do?

A

1 = rRNA - most numerous

2 = mRNA - massive

3 = tRNA - tiny

No proofreading funciton

RNA Pol 2 opens DNA at promoter site

22
Q

What gets added to molecules so that they are trafficked to lysosomes? When does this go awrdy?

A

Mannose-6-Phosphate added in Golgi to proteins that go to lysosomes

I CELL DISEASE = inherited lysosomal storage disorder

  • defect in N-actylglycosaminyl-1phosphotransferase –> Failure of Golgi to phosphorylated mannose resudese on glycoproteins so they are excreted extracellulary instead of delivered to lysosome

Coarse Facial Features, Clouded Corneas, Restricted joint movement an hihg plasma lysosomal enzymes

23
Q

What are immunohistochemical stains for intermediate filaments?

A

Vimentin - CT

DesMin - Muscle

Cytokeratin - epithelial

GFAP - neuroGLIA

Neurofil - neurons

24
Q

Drugs that act on Microtubules?

A

Microtubules Get Constructed Very Poorly

Mebendazole

Griseofulvan

Colchicine

Vincristine/Vinblastine

Paclitaxel

25
Q

DIseases of Collagen synthesis (4) - what are they and at what steps?

A

1) Scurvy - Vit D deficiency and so can’t hydroxylate proline and lysine in RER
2) OI - can’t form tripe helix from glycosylation of procollagen and disulfide bonds in RER
3) Ehlers Danslos- can’t crosslink Collagen fibrils in ECM
4) Menkes Disease - Cant absorb copper which is needed for lysyl oxidase to crosslink collagen fibrils

26
Q

Menkes DiseaSE?

A

XL Recessive CT disease bc imapired copper absorption and transport from defective ATP7A Menkes Protein

Decreased activity of Lysyl Oxidase and so brittle kinky hair, grwoth retardation and hypotonia

27
Q

What is Elastin? What diseases include elastin problems?

A

Stretchy protein rich in NON-HYDROXULATED glycine, proline, and lysine

Tropoelastin w/ Fibrillin scaffolding

Broken down by Elastase which is inhibited by Alpha1 Antitrypsin

MARFAN - defect in Fibrillin and so no sheath around elastin

Emphysema = A1AT deficiency and so increased elastsase degradation

28
Q

Describe the 4 kinds of blotting procedures?

A

SNoW DRoP

Southern = DNA

Northern = RNA - gene expression

Western = Protein (ex. confirmatory test for HIV after ELISA)

Southwestern - DNA binding proteins (transcription factors)

29
Q

Difference between Direct and Indirect Elisa?

A

Direct - Test antibody to see if antigen is present

  • antibody directly coupled to color changing enzyme

Indirect - test antigen or antibody to see if specific antibody is present

  • secondary antibody couplets to color-generating enzme
30
Q

What is Mosaicism? Types? Disease associated w/ it?

A

presence of Genetically distinct cells lines in same individual

Somatic Mosaicism - mutation from mitotic errors after fertilization and propogates through multiple tissues

Gonadal Mosaicism - mutation only in egg or sperm cells

McCune Albright Syndrome!!!

31
Q

Findings ni Down Syndrome by trimester>?

A

First Trimester - increased Nuchal translucency and hypoplastic nasal bone

Serum PAPP-A is decreased and free beta-HCG is increased

Second Trimester - decreased AFP and Estriol

Increased Beta HCG and Inhibin A

32
Q

Water Soluble Vitamines are?

Which ones do not wash out of body easily?

A

B1 = Thiamine TPP

B2 = Riboflavin FAD/FMN

B3 = Niacin - NAD+

B5 = Pantothenic Acid - CoA

B6 = Pyridoxine - PLP

B7 = Biotin

B9 = FOLATE

B12 = Cobalamin

C = Ascorbic Acid

33
Q

What are the symptoms/results of B complex Deficiencies?

A

Dermatitis

Glossitis

Diarrhea

USMLE Studying (8 decks)

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