Mod 7: Protein synthesis Flashcards

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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

A

:)

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
Q

what happens once the release factor is bound

A

hydrolysis of polypeptid chain from tRNA and chain released and tRNA dissociates

26
Q

what is GTP

A

guanosine triphosphate

27
Q

what does GTP do

A

provides energy (via hydrolysis) GTP -> GDP + Pi

most initiation factors, elongation factors and release factors are bound covalently to GTP