Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biol 200 > Lecture 19 - Translation (pt 2) > Flashcards

Lecture 19 - Translation (pt 2) Flashcards

1
Q

3 sites on ribosome and the corresponding tRNA

A 
A site (Amino acyl) for aminoacyl tRNA. 
P site (Peptidyl) for Peptidyl tRNA
E site (Exit)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How peptide bond between 2 a.a forms in ribosome and where goes the polypeptide chain

A

N on N-terminal part of the next a.a. attacks the carbon on the carboxy terminal part of the previous a.a. Chain goes on the amino acyl tRNA. It moves to the P site and moves the mRNA with it and becomes the peptidyl tRNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Structure of the ribosome and important thing to remember about process of translation discussed

A

One large subunit and one small subunit. Translation discussed is about protein synthesis in EUKARYOTES.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why translation is complex

A

Because you have to get the specific sequence for each protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What initiation phase of eukaryotic translation consists of

A

Assembly of ribosome with an mRNA and an initiator tRNA charged with methionine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What elongation phase of eukaryotic translation consists of

A

Stepwise addition of a.a. to the polypeptide chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What termination phase of eukaryotic translation consists of

A

Release of completed polypeptide and release of ribosome. Disassembly of the ribosome.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What tRNA is needed to start synthesis of the polypeptide chain

A

tRNAi Met

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Two types of tRNAs for the methionine codon, their function and their specific aminoacyl tRNA synthetase

A

1) tRNAi Met (initiator)
2) tRNA Met (regular one - for Met in middle of the protein)
Charged with the same aminoacyl tRNA synthetase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

tRNA i Met in eukaryotes, archaeans and bacteria

A

Eukaryotes and Archeans -> tRNA i Met + methionine —> Met - tRNA i Met
Bacteria -> tRNA i Met + methionine + FORMYL GROUP (CHO) —-> fMet-tRNA i Met

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Something particular about the chemical modifications of the first methionine in bacteria

A

It can be recognized by our cells as foreign.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

tRNA Met (regular one) in eukaryotes, archaeans and bacteria

A

tRNA Met + methionine —> Met - tRNA Met

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens to Met when protein synthesis is finished

A

All proteins start with Met when they are made but Met can be changed/removed later.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Formation of 43 S preinitiation complex - 1st step

A

tRNA i - Met (charged with Met ) binds eIF2 carrying GTP to form the eIF2 ternary complex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

T/F : mRNA joins 43 S preinitiation complex

A

False . No mRNA at this step

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What eIF# stands for

A

eukaryotic initiation factor 1,2,3, etc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is a GTPase (2 things)

A
  1. small molecules that can have 2 shapes depending on if they bind GTP or GDP
  2. Can hydrolize GTP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

eIF2 precise function. Does it take part in the complex ?

A

Not part of the translation machine but acts as a regulatory component

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Important concept in translation

A

Regulatory checkpoints

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What 40 S contains (4)

A
  1. Small ribosomal subunits with E, P, A site
  2. eIF3 that binds to small ribosomal subunit near E site
  3. eIF1 binds E site
  4. eIF1A binds A site
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Formation of 43 S preinitiation complex - 2nd step

A

eIF2 ternary complex, 40 S and eIF5 join to form 43 S complex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What 43 S complex contains

A

40 S with 1) ternary complex (tRNAi - Met bound to eIF2 - GTP) on the P site
and 2) eIF5 bound to eIF1 (that is bound to E site)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How can protein synthesis be negatively regulated and how it works

A

phosphorylation of eIF2 on different residues makes it keep GDP. GDP and GTP bind the same site on it so it affects its ability to bind GTP (switch from GDP to GTP = becomes active)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What eIF4 complex contains

A

4E, 4G, 4A (and 4B - when it binds the mRNA)

25
Q

What mature mRNA ready for translation initially contains

3

A

1) 5’ cap
2) Start and stop codon
3) Poly(A) tail bound by PABPC

26
Q

How mRNA activation works

A

eIF4 complex (and 4B) binds to mRNA

27
Q

Near what region eIF4 complex binds on mRNA

A

near 5’ cap

28
Q

What eIF4E binds to

A

5’ cap structure

29
Q

What eIF4G binds to

A

PABPC (which is bound to Poly(A) tail)

30
Q

What eIF4A and eIF4B do

A

eIF4A RNA helicase unwinds RNA secondary structure at 5’ end. eIF4B joins and stimulates helicase activity

31
Q

Note about secondary structure at 5’ end of mRNA

A

Not necessarly present

32
Q

Why does mRNA activation reaction (eIF4 complex (and 4B) binds to mRNA ) requires ATP/phosphorylates ATP

A

ATP is required to unwind RNA secondary structure at 5’ end if present, by eIF4A RNA helicase

33
Q

Attachement of 43S preinitiation complex to mRNA how it happens

A

eIF3 (bound to small ribosomal subunit near E site) interacts with eIF4 (on 5’ region of mRNA)

34
Q

Step after Attachement of 43 S preinitiation complex to mRNA and how it works

A

Scanning from 5’ to 3’. mRNA is pulled in the groove of the small ribosomal subunit until tRNAi sees AUG.

35
Q

What happens after recognition of AUG by tRNAi and what does that do

A

eIF2 recognizes that this happened and hydrolizes GTP to GDP (release of Pi). This causes scanning to stop.

36
Q

What is 48 S intitiation complex.

A

43 S with the mRNA, the tRNA i recognizing the AUG and eIF2 bound to GDP

37
Q

Recruitment of large ribosomal subunit. Its name, its regions and what happens when it binds 48 S

A

60 S. Regions complementary to E, P and A site. When it binds 48 S, 5B-GTP binds 1A (bound to A site) and displacement of eIF1, 2-GDP, 3, 4 (E,G,A and B) and 5

38
Q

What is left after recruitment of large ribosomal subunit (4)

A

2 ribosomal subunits with E, P and A site.
RNAi - Met recognizing AUG at P site.
1A bound to A site and 5B-GTP.
The mRNa.

39
Q

What steps follows large ribosomal subunit binding (2). What’s the name of the complex formed. What this causes

A
  1. Hydrolysis of GTP on eIF5B.
  2. Release of eIF5B bound to GDP and release of eIF1A
    This forms the 80 S initiation complex. It can no longer dissociate and is committed to translation
40
Q

Condition for hydrolysis of GTP on eIF5B

A

Large ribosomal subunit must bind correctly (fits right). Other large subunit that don’t fit right come and leave. Hydrolysis of GTP on eIF5B marks the correct fitting and dissociation can no longer happen.

41
Q

What the 80 S initiation complex contains

A
  1. Ribosome and its 3 sites E, P, A
  2. mRNA
  3. tRNA i Met - Met recognizing AUG
42
Q

After 80 S initiation complex is obtained, what triggers translation elongation

A

Entry of charged tRNAs bound to EF1alpha ( ELONGATION FACTOR 1 ALPHA) on A site. When right tRNA enters, GTP on EF1alpha is hydrolized

43
Q

GTP on EF1alpha hydrolysis reaction and what happens to the ribosome (2)

A

EF1alpha-GTP –> EF1alpha-GDP + Pi.
These products are RELEASED and this causes
1) a conformational change in the ribosome and
2) a reposition of the tRNA on A site -> tRNAs become adjacent and peptide formation can start

44
Q

What catalyzes the first peptide bond formation. What is the reaction called and what is the product obtained and what does it contain.

A

Catalyzed by large ribosomal RNA. Reaction called peptidyltransferase reaction. Oligopeptide obtained contains Meti and aa2

45
Q

After first peptide bond formation, translocation happens. (and happens after each peptide bond formation). What happens during translocation

A

Ribosome moves along mRNA a distance of one codon.

tRNA i moves to E site, tRNA aa2 moves to P site, A site is vacant.

46
Q

What is necessary for translocation to happen (it is essential a physical displacement in the ribosome)

A

EF2 - GTP must recognize successful elongation. It hydrolyzes GTP and EF2 - GTP + Pi is obtained. This makes the step irreversible

47
Q

First step of translation termination

A

No tRNA binds the stop codon. Instead, eRF1 (eukaryotic release factor 1) bound to eRF3-GTPase goes to the A site.

48
Q

Second step of translation termination

A

eRF3 - GTP HYDROLYSIS acts with eRF1 to promote cleavage of the peptidyl-tRNA, releasing the finished polypeptide. (Pi is obtained)

49
Q

What do we call the complex formed after release of the polypeptide and what is bound to eRF1 at this point

A

Post-termination complex. eRF3-GDP is bound to eRF1.

50
Q

How are the subunits of the ribosome and the mRNA all seperated

A

IN A PROCESS USING ATP (ATP - ADP + Pi), ABCE1 binds the post-termination complex and separates the ribosomal subunits

51
Q

What happens to small ribosomal subunit after seperation of the ribosome (what is released (3) and what binds to it (3))

A

P tRNA, eRF1 and eRF3-GDP are released (they’re all seperated)
eIF1, eIF1A and eIF3 bind to small ribosomal subunit again.

52
Q

Elongation rate characteristics (2)

A
  1. Relatively constant elongation rate.

2. Typical protein molecule takes 30-60 sec. to synthesize

53
Q

What do we call multiple ribosomes

A

polysomes

54
Q

First way of maximizing rate of translation

A

Simultaneous translation from the same mRNA by multiple ribosomes (polysomes)

55
Q

Second way of maximizing rate of translation

A

Efficient reinitiation and efficient recycling of ribosomal subunits

56
Q

How can the mRNA take a circular form during translation

A

Interaction of factors that bind the 5’ (eIF4G) with factors that bind the 3’ Poly(A) tail (PABPC)

57
Q

How circular shape of mRNA can make reinitiation and ribosomal subunits recycling more efficient

A

Upon termination, ribosome subunits will be close to the mRNA 5’ end (this enhances reinitiation)

58
Q

Names of the large and small ribosomal subunits when they are released and before any translation initiation

A

Small ribosomal subunit = 40S

Big ribosomal subunit = 60S

59
Q

What allows monitoring and checkpoints of individual steps in translation

A

GTPases that hydrolize GTP and cause irreversible conformational changes in the complex.

Biol 200 (30 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions