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metabolism year 2 > DNA translation > Flashcards

DNA translation Flashcards

1
Q

what is translation

A

the synthesis of a linear chain of amino acids (primary transcript)

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2
Q

what does translation require

A

aminoacyl-tRNA
ribosomes
mRNA

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3
Q

what is the site of translation

A

ribosomes

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4
Q

functional 80S ribsomoe is composed of what

A

2 subunits

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5
Q

what subunits are contained by a large 60S subunit

A

5S rRNA- 120 nucleotides
28S rRNA- 2,700 nucleotides
5.8S rRNA- 160 nucleotides
about 49 ribosomal proteins

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6
Q

what does a small 40S subunit contain

A

18S rRNA
about 33 ribosomal proteins

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7
Q

what fit together to form a cleft

A

the 2 irregularly shaped subunits (40S and 60S)

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8
Q

how do the mRNA and cleft interact

A

mRNA moves through the cleft as the ribosome passes along the mRNA during translation

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9
Q

where is mRNA bound

A

to the small 40S subunit

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10
Q

how many binding sites does the 60S subunit contain

A

2

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11
Q

what are the binding sites on the 60S subunit called

A

P site and A site

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12
Q

what is the purpose of the P site on the 60S subunit

A

growing polypeptide chain is bound to this site (peptidyl-tRNA site)

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13
Q

what is the purpose of the A site on the 60S subunit

A

new aminoacyl-tRNA to be added to growing polypeptide chain is bound at this site (aamino-tRNA site)

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14
Q

what does translation proceed from and to

A

N-terminus to C-terminus of protein

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15
Q

what direction is mRNA read in

A

5/ to 3/

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16
Q

how many ribosome can be bound and translated to mRNA at the same time

A

more than one

17
Q

what is translation also known as

A

protein synthesis

18
Q

how does chain elongation occur

A

by addition of amino acids to C-terminal of the polypeptide bound to the ribosome

19
Q

what happens during the initiation phase in relation to proteins

A

begins with the binding of the initiation protein eIF3 to the 40S ribosomal subunit
this protein acts as an anchor for other initiation proteins which ultimately bind the mRNA to the 40S ribosomal subunit
eIF3 binds another protein, called eIF4G which contains two further protein binding sites on it
eIF4G binds ployA binding protein (PAB)
PAB is bound to the polyadenylated 3/-end of the mRNA molecule

20
Q

what proteins are involved in the initiation phase

A

eIF3, eIF4G, PloyA binding protein

21
Q

what happens in the initiation phase after the protein binding

A

once bound to the 40S ribosomal subunit, the mRNA nucleotide sequence is scanned from the 5/ end until the initiation codon sequence is encountered (5/-AUG)
the 60S ribosomal subunit is attached to the 40S ribosomal subunit forming the initiation complex. the methionine-tTRNA occupies the P site

22
Q

what happens during elongation

A

aminoacyl-tRNA occupies A site
A peptide bond is now formed between the 2 amino acids in the P and A site
transfer of amino acid occupying P site onto aminoacyl-tRNA occupying A site
a-amino group of amino acid in A site attacks carboxyl group of amino acid in P site, displacing bond with tRNA at P site

23
Q

what happens during translocation

A

ribosome moves one codon towards 3/-end of mRNA. movement requires the action of a translocase (elongation factor)
movement shifts anticodon of peptidyl-tRNA occupying A site into P site and and tRNA occupying P site is released
A site is now empty, awaiting new aminoacyl-tRNA

24
Q

what are the 3 termination sequences

A

UAA
UAG
UGA

25
Q

what happens when a termination sequence occurs

A

it is recognized by a release factor called eRF

26
Q

what 3 things does eRF do

A

hydrolyses terminal peptidyl-tRNA bond
releases free polypeptide and tRNA from the P site
Ribosome dissociates into 40S and 60S subunits

27
Q

what are the 4 phases of translation

A

initiation
elongation
translocation
termination

metabolism year 2 (24 decks)

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