Translation

Question 1

Translation

Answer 1

Biosynthesis of proteins based on mRNA

Question 2

What is needed for translation

Answer 2

• mRNA
• tRNA
• Ribosomes
• Protein factors

Question 3

Function of: mRNA

Answer 3

Carries genetic information

Question 4

Function of: tRNA

Answer 4

Transports activated amino acids for translation

Question 5

What process takes place in the ribosome?

Answer 5

Translation

Question 6

What forms the structure of tRNA?

Answer 6

Intramolecular base pairing

Question 7

Give the three loop types found in tRNA

Answer 7

• DHU-loop
• Anticodon-loop
• TφC-loop

Question 8

DHU-loop binds…

Answer 8

Aminoacyl-tRNA-synthetase

Question 9

Anticodon-loop binds…

Answer 9

Codons of mRNA

Question 10

TφC-loop binds

Answer 10

The large subunit of the ribosome

Question 11

The T in the TφC-loop represents…

Answer 11

Thymidine-monophosphate

Thymine in RNA

Question 12

The φ in the TφC-loop represents…

Answer 12

Pseudouridine-monophosphate

Question 13

Describe the binding of a tRNA with an amino acid

Answer 13

• CCA-sequence (3’-end) of tRNA

Binds to

• Carboxyl group of amino acid

Question 14

How are amino acids activated?

Answer 14

Binding of the adequate amino acid with the tRNA

Question 15

Name the enzyme which binds the amino acid to its specific tRNA

Answer 15

Aminoacyl-tRNA-synthetase

Question 16

Aminoacyl-tRNA-synthetase binds…

Answer 16

ATP

Question 17

Give the reaction of amino acid binding to tRNA

Answer 17

1. ATP + Amino acid → Aminoacyl-AMP + PP_i
2. Aminoacyl-AMP + tRNA → Aminoacyl-tRNA + AMP

Question 18

Aminoacyl-tRNA-synthetase binds to which part of tRNA?

Answer 18

DHU-loop

Question 19

Give the structure of a ribosome

Answer 19

• Proteins
• Ribosomal RNA (rRNA)
  
  • Large subunit
  • Small subunit

Question 20

Different types of rRNA can be characterised by their…

Answer 20

• Sedimentation coefficient
• Unit: Svedberg = S

Question 21

Give the binding sites of large ribosomal subunits

Answer 21

• A-site
• P-site
• E-site

Question 22

A-binding site

Answer 22

Aminoacyl-tRNA binding site

Question 23

P-binding site

Answer 23

Peptidyl-tRNA binding site

Question 24

E-binding site

Answer 24

Exit

Question 25

Give the binding site of small ribosomal subunits

Answer 25

mRNA-binding site

Question 26

In eukaryotes, translation occurs in the...

Answer 26

* Cytoplasm * RER (membrane with ribosomes)

Question 27

Summarise the steps of initiation in eukaryotes

Answer 27

1. Pre-initiation complex 2. Kozak-scanning mechanism 3. Recognised start codon 4. Initiation complex

Question 28

Give the composites of the _pre-initiation complex_

Answer 28

* Small ribosomal subunit * eIF-2-GTP * other eIF-S * tRNA_Met

Question 29

Kozak-scanning mechanism

Answer 29

* Pre-initiation complex rolls along mRNA strand * Locates the start codon (AUG)

Question 30

_Recognised start codon_ stage

Answer 30

_Small ribosomal subunit_ binds to _Kozak-sequence of mRNA_

Question 31

Give the formation of the initiation complex

Answer 31

1. Hydrolysis of the GTP bound to eIF-2 → GDP + P_i 2. Large ribosomal subunit binds to the small 3. All eIF-s dissociate

Question 32

What occurs at the end of initiation

Answer 32

* Methionyl-tRNA binds *via TφC-loop to* P-site of the large subunit * A-site of the large ribosomal subunit is free

Question 33

Steps of elongation of translation in eukaryotes

Answer 33

1. Binding of aminoacyl-tRNA to A-site of large ribosomal subunit 2. Methionine moved from methionyl-tRNA onto the newly bound aminoacyl-tRNA 3. Translocation

Question 34

Describe binding of aminoacyl-tRNA to A-site of the large ribosomal subunit

Answer 34

* EF-1α + GTP complex needed * _Aminoacyl-tRNA_ binds to: * The _A-site of large RSU_ *via TφC-loop* * The next codon of mRNA *via its anticodon loop*

Question 35

Describe methionine placement onto the aminoacyl-tRNA

Answer 35

* Catalysed by Peptidyl-transferase * A new peptide bond is formed between: * Methionine * Newly bound amino acid * Forms a dipeptidyl-tRNA * The 'empty' tRNA moves from P-site to the E-site * It then dissociates

Question 36

Translocation stage of eukaryotic translation

Answer 36

* Dipeptidyl-tRNA placed onto the P-site * Catalysed by translocase * Requires: * EF-2 * GTP complex

Question 37

Describe the end stage of eukaryotic translation

Answer 37

* Dipeptidyl-tRNA binds to the P-site of the large RSU *via TφC-loop* * A-site of the large ribosomal subunit is free

Question 38

Describe termination of translation in pro- and eukaryotes

Answer 38

* Stop codon: no aminoacyl-tRNA can bind to A-site * PRF protein binds to A-site instead * Deliberation of the newly synthesised protein chain * By dissociation of ribosomal subunits

Question 39

Initiation phase of translation in prokaryotes

Answer 39

1. Small RSU + IF-1 and IF-3 2. 30S initiation complex formation 3. 70S initiation complex

Question 40

30S initiation complex is formed by

Answer 40

* Small ribosomal subunit + IF-1 and IF-3 * + IF-2-GTP + tRNA_ini + mRNA

Question 41

How is the 70S initiation complex formed

Answer 41

1. IF-1 and IF-3 dissociate 2. GTP hydrolyses 3. Large RSU binds

Question 42

List the major differences between the prokaryote and eukaryote stage of initiation

Answer 42

* 3 IF-s are needed for prokaryotes, Eukaryotes need more * Initiator amino acid: _N-formyl-methionine_ in prokaryotes * No Kozak-scanning mechanism in prokaryotes

Question 43

Give the elongation stage of prokaryotic translation

Answer 43

* Different elongation factors: * EF-Tu; EF-G * Transcription + translation happen simultaneously * One mRNA binds to more than one ribosome * Polyribosome

Question 44

What is shown in the figure

Answer 44

Polyribosome

Question 45

Energy requirement of: Initiation

Answer 45

1 GTP

Question 46

Energy requirement of: Kozak-scanning mechanism

Answer 46

1 ATP

Question 47

Energy requirement of: Elongation

Answer 47

4 ATP

Question 48

Energy requirement of: Termination

Answer 48

1 GTP