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Molecular biochem Flashcards

1
Q

What pathway is CPS I (carbamoyl-phosphate-synthetase) used in? Location? Nitrogen source

A

Urea cycle. Mitochondria. Ammonia

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2
Q

What pathway is CPS II (carbamoyl-phosphate-synthetase) used in? Location? Nitrogen source

A

Pyrimidine synthesis (rate limiting step). Cytosol. Glutamine.

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3
Q

What is the rate limiting step in purine synthesis?

A

PRPP amidotransferase

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4
Q

What is the rate limiting step in pyrimidine synthesis?

A

CPS II (carbamoyl-phosphate-synthetase)

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5
Q

**What are the sources of carbons in the formation of purines?

A

Glycine, CO2, Tetrahydrofolate. Aspartate and glutamine are also essential (donate nitrogens)

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6
Q

**What are the carbon sources in pyrimidine synthesis?

A

Aspartate and CO2. (CO2 and glutamine form carbamoyl phosphate).

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7
Q

What accounts for the positive charge of histones.

A

Lysine and Arginine

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8
Q

What accounts for the negative charge of DNA

A

phosphate groups on nucleoTides (vs nucleosides which are simply base + ribose)

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9
Q

How many adenine residues are found in a molecule of DNA if one strand contains A =2000, G = 500, C= 1500, and T= 1000.

A

3000 (2000 on this side, plus 1000 on the other since there are 1000 T’s)

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10
Q

What strand of DNA nucleotides opposes the strand 5’ ATTGCGTA 3’

A

TACGCAAT (3’ TAACGCAT 5’). MUST MAKE SURE TO WRITE IT 5’ ->3’

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11
Q

Which med? Inhibits ribonucleotide reductase

A

Hydroxyurea

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12
Q

Which med? Inhibits dihydrofolate reductase

A

Methotrexate and trimethoprime

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13
Q

Which med? inhibits PRPP synthetase

A

6-MP

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14
Q

Which med? inhibits inosine monophosphate dehydrogenase

A

Mycophenylate

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15
Q

Which med? inhibits thymidylate synthase

A

5-FU

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16
Q

What are the characteristic features of orotic aciduria?

A

Orotic acid in the urine. Megaloblastic anemia that is not correctable with vitamin B12 or folate. Failure to thrive. No elevated blood levels of ammonia. (**Autosomal recessive, UMP synthase defect -> accumulation of orotic acid)

17
Q

**How does UV light damage DNA?

A

Causes a thymine-thymine bond on the same strand of DNA (thymine dimer). Not on complementary strands.

18
Q

Which eukaryotic DNA polymerase replicates lagging strand and synthesizes RNA primer?

A

DNA polymerase alpha

19
Q

Which eukaryotic DNA polymerase repairs DNA?

A

DNA polymerase beta/ epsilon

20
Q

Which eukaryotic DNA polymerase replicates mitochondrial DNA?

A

DNA polymerase gamma

21
Q

Which eukaryotic DNA polymerase replicates leading strand DNA?

A

DNA polymerase delta

22
Q

Which antibiotic(s)? Inhibits the 50s peptidyltransferase

A

Chloramphenicol and streptogramins

23
Q

Which antibiotic(s)? binds 50s blocking translocation

A

Macrolides, linezolide

24
Q

Which antibiotic(s)? bind 30s, preventing attachment of the tRNA

A

Tetracyclines

25
Q

Which antibiotic(s)? inhibits prokaryotic RNA polymerase

26
Q

Which antibiotic(s)? inhibits prokaryotic topoisomerase

A

Fluoroquinilones

27
Q

Which antibiotic(s)? inhibits prokaryotic dihydrofolate reductase

A

Trimethoprim (methotrexate does also but is a immunosuppresent/ anticancer drug)

28
Q

What are three different mechanisms cells employ to break down proteins

A
  1. Ubiquitin tagging with ubiquitin protein ligase degradation
  2. Lysosome
  3. Ca++ enzyme
29
Q

What enzyme catalyzes peptide bond formation during protein synthesis?

A

Peptidyl transferase (ribozyme = 23s rRNA)

30
Q

What enzyme matches amino acids to tRNA?

A

Aminoacyle-tRNA synthetase

31
Q

What are the mRNA stop codons?

A

UGA, UAA, UAG (You go away, you are away, your are gone)

32
Q

what are the different RNA polymerases in eukaryotes?

A

RNA polymerase I -> codes for rRNA
RNA polymerase II -> transcribes mRNA
RNA polymerase III -> codes for tRNA

33
Q

What amino acid typically has more coding sequences in the mRNA than are represented in the peptide that is created from that mRNA?

A

Methionine

34
Q

**How is hnRNA processed before it leaves the nucleus

A

Gets a 5’ cap, poly A tail and introns spliced out

35
Q

What is the characteristic sequence of the promotor region? What does a mutation in the sequence cause?

A

TATA box (-25 nucleotides) and CAAT box (-75 nucleotides). Mutation will decrease amount of gene transcription

36
Q

What enzyme is deficient in Lesch-Nyhan syndrome? Tx?

A

HGPRT. Allopurinol

37
Q

What structural motifs allow for proteins to bind to DNA?

A
  1. Helix loop helix
  2. Helix turn helix
  3. Zinc finger
  4. Leucine zipper

Biochem (8 decks)

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