Mod 7: Protein synthesis Flashcards

1
Q

in prokaryotes, what type of ribosome and what subunits are they made up of

A

70s ribsomes

Large subunit = 50s = 23s rRNA + 5s rRNA + 31 proteins

Small subunit = 30s = 16s rRNA + 21 proteins

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2
Q

in eukaryotes, what type of ribosome and what subunits are they made up of

A

80s ribosomes

Large subunit = 60s =
28s rRNA + 5.8s rRNA + 6s rRNA +48 proteins

Small subunit = 40s =
18s rRNA + 33proteins

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3
Q

what does s stand for in the sixing of ribosomes

A

Svedberg
a measure of sedimentation rate of suspended particles centrifuged (in standard conditions)

not determinant of the mass of molecule but the shape and size

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4
Q

what needs to happen before AA can bind to DNA?

A

must bind with ATP first

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5
Q

what process allows AA to bind with ATP and explain x

A

transesterification

hydroxyl group from the carboxy end of an AA is lost and is joined onto ATP
which leads to loss of 2 phosphates (gamma and beta)
1 remains (alpha)

leaves amino acyl AMP

this then gets joined to the correct tRNA at the tRNA 3’ acceptor arm

see onenote

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6
Q

initiation - whawt is Shine-Dalgarno sequence

A

sequence of bases with AUG (methionine initiator codon) embedded

used to recognise and pair w/ 30s subunits
specifically the 16s ribosomal RNA, which scans the mRNA until it finds this sequence and binds

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7
Q

what is the equivalent to the Shine-Dalgarno sequence in eukaryotes

A

Kozak sequence

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8
Q

how many tRNAs are there for methionine and what are their functions

A

one for initiation (to start translation)
one for elongation (so within the gorwing polypeptide chain)

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9
Q

for process of translation and diagram, see onenote

A

:)

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10
Q

what are the initiation factors involved in translation

A

IF1
IF2
IF3

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11
Q

IF1 function

A

makes sure the tRNA only binds to large subunit on correct side (P site)
cuz theres 2 sides, and IF1 blocks the A site

also inhibits premature interaction between 30s and 50s

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12
Q

IF2 function

A

tags the initiator tRNA and regulates its entry into ribosome

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13
Q

IF3 function

A

stops premature association of 30s and 50s

stabilises free 30s

accuracy check to make sure tRNAi-met is bound in the right place

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14
Q

Elongation:

what site does the tRNAi Met associate with on the large subunit

A

the P site

this is the only one that can do this

other amino acyl tRNAs that are involved in elongation associate with A site

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15
Q

what does the A site do

A

where new amino acyl tRNAs come and slot in during elongation

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16
Q

what does the A site do

A

where new amino acyl tRNAs come and slot in during elongation

remember it by A for amino acyl idk

17
Q

what is the elongation factor that brings in the amino acid

A

EFTu
coupled with GTP

so it forms a aminoacyl tRNA-EFTU-GTP complex

18
Q

once the new aminoacyl tRNA binds, what is ejected

A

EF-TU-GDP (so it’s been converted from GTP, but this will be recycled and goes back into process)

19
Q

what kind of bond forms between the AAs

A

peptide bond duh

20
Q

what happens when peptid bond gets formed

A

first tRNA (tRNAi Met) gets ejected from P site

21
Q

what is the other accessory factor involved in translocating the ribosome along the mRNA strand

A

EF-G-GTP

which then turn into EF-G-ADP after it’s ejected

22
Q

recap then, what are the 2 elongation factors and their functions

A

EF-Tu
mediate aminoacyl-tRNA entry into ribsome

EF-G mediates translocation

23
Q

see onenote for diagram and deatil on elongation

24
Q

Termination:
what are the release factors used in this process and their functions

A

RF1 = recognises UAA/UAG
RF2= recognises UAA/UGA
RF3= helps the other 2 bind to the ribosome (coupled with GTPase, so is a G protein)

25
what happens once the release factor is bound
hydrolysis of polypeptid chain from tRNA and chain released and tRNA dissociates
26
what is GTP
guanosine triphosphate
27
what does GTP do
provides energy (via hydrolysis) GTP -> GDP + Pi most initiation factors, elongation factors and release factors are bound covalently to GTP