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biochem 2 > Life of Proteins > Flashcards

Life of Proteins Flashcards

1
Q

monocistronic

A

one ORF per mRNA

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2
Q

polycistronic

A

mRNA codes several ORFs

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3
Q

eukaryotic mRNA is ____, prokaryotic mRNA is _____

A

monocistronic

polycistronic

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4
Q

where do tRNA anneal to 3-base codons on the mRNA

A

3-base anticodon region

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5
Q

what do tRNAs have at acceptor terminus

A

amino acid

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6
Q

how many possible codon sequences are there

A

64

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7
Q

wobble hydpotsis

A

position of of the anticodon is flexible and can wobble to pair with different nucletodies in the 3rd position of the codon

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8
Q

what does tRNA have that isn’t found in DNA or mRNA

A

inosine

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9
Q

how are tRNA molcules linked to amin oacid

A

aminoacyl-tRNA synthases

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10
Q

how many aminoacyl tRNA synthetases are there

A

20

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11
Q

where does translation take place

A

cytosol on ribosomes

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12
Q

how many subunits do ribosomes have

A

2

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13
Q

how many RNA molecules are found in ribosomal subunitns

A

1-3

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14
Q

function of cytoplasmic ribosomes

A

synthesis of the bulk of proteins

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15
Q

function of mitochondrial ribosomes

A

protein sythesis inside of mitochondria

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16
Q

where are ribosomal subunits syntehsied

A

cytosol

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17
Q

intiation of translation requires the correct assumbly of waht

A
  • small ribosomal subunit
  • mRNA
  • tRNA that binds the first codon
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18
Q

what happens once the small subunit is laoded with tRNA and mRNA

A

binds to large subunit to conclude insitation phase

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19
Q

first step of intiation

A

elF2a activated by binding GTP

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20
Q

what does elF2a-GTP do

A

binds intiator methionine-tRNA met to form ternary compelx

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21
Q

what does ternay complex do

A

bind small ribosomal suunit

22
Q

what happens to the small ribosomal subunit

A

mRNA binds to it, forming pre-initiation complex

23
Q

what does pre-initaition compelx do

A

assembles into initation complex by binding large ribosomal subunit

24
Q

how does elongation phase starte

A

initation methionine tRNA met binds to P site of ribosome

25
Q

what happens after initatior methionine tRNA met binds to P site

A

second aminoactyl-tRNA placed into A site which requies EF-1

26
Q

what happens after the aminoacyl-tRNA is placed on the A site

A

peptidyl bond formed btwn 1st and 2nd amino acid

27
Q

what happens after the peptidyl bond forms

A

ribosome moves one codon further on mRNA with help from EF-2. now mRNA-peptidyl complex is in P site and A site is empty. uncharged tRNA levels through E site

28
Q

how does termination start

A

stop codon reaches A site of ribosome

29
Q

what happens after ribosome reaches A site

A

eRF pairs with stop codon

30
Q

what happens after eRF pairs with stop codon

A

eRF bound GTP is hydrolyzes and peptides is released from P site

31
Q

how does streptomycin work

A

binds to small subunit and inhibitis initiation

32
Q

how does neomycin and gentamicin work

A

bind to ribosomes and cause mistranslation of codonds

33
Q

how does tetracycline work

A

block A site, prevents tRNA binding

34
Q

how does chloramphenicol work

A

prevent peptidyl bond formation

35
Q

how does riicin work

A

removes adenine bases from various positions of the rRNA in the alrge subunit

36
Q

how do you regulate transctation

A

prevent recognitino of start codon

regulat acitivity of initaiton factors

37
Q

how do chaperones work

A

binding to hydrophobic regions of the folding peptide

38
Q

where are chaperons foudn

A

cytosol and ER

39
Q

Charcot Marie Tooth Disease is caused by what

A

mutation in HSP gene

40
Q

what happens to cells during the unfolded protein response

A

inhibit global protein translation
induce chaperone production
apoptosis

41
Q

what does glycosylation do

A

changes the physical properties of proteins

42
Q

where does glycosylation of proteins take place

A

begin in ER, continue into golig

43
Q

reaction of glycosylation

A

glycosyltransferase transfers sugar from activiated sugar nucleotide to acceptor substrate

44
Q

what are the glycosyltransferases specific for

A
  • the sugar donor
  • the acceptor molecule
  • type of glycosidic bond formed
45
Q

what happens during N linked glycosylation

A

an oligosaccharide molecule is added to tha mino group of an aspargine residue

46
Q

steps of N linked glycosylation

A

1) synthesis of univeral oligosaccharide on dolichol phostate in ER
2) transfer of univeral oligosaccharide to nascent polypeptide chain
3) modification of univeral oligosaccharide in golgi

47
Q

O-linked glycosylation

A

post translation event, only occurs on fully folded proteins. only occurs after protein has reached golgi

48
Q

step of O link glycosylation

A

glycosyltransferases of goligi transfer N-acetyl-galactosamine to hydroxyl group of serine or threonine rediues on surface of protein

49
Q

what is O linked glycosylation involved in

A

blood typing

50
Q

how can proline be modified

A

hydroxylated to function in colalgen triple helix

biochem 2 (22 decks)

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