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Biochemistry > Translation > Flashcards

Translation Flashcards

1
Q

Translation

A

Biosynthesis of proteins based on mRNA

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2
Q

What is needed for translation

A
  • mRNA
  • tRNA
  • Ribosomes
  • Protein factors
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3
Q

Function of: mRNA

A

Carries genetic information

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4
Q

Function of: tRNA

A

Transports activated amino acids for translation

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5
Q

What process takes place in the ribosome?

A

Translation

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6
Q

What forms the structure of tRNA?

A

Intramolecular base pairing

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7
Q

Give the three loop types found in tRNA

A
  • DHU-loop
  • Anticodon-loop
  • TφC-loop
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8
Q

DHU-loop binds…

A

Aminoacyl-tRNA-synthetase

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9
Q

Anticodon-loop binds…

A

Codons of mRNA

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10
Q

TφC-loop binds

A

The large subunit of the ribosome

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11
Q

The T in the TφC-loop represents…

A

Thymidine-monophosphate

Thymine in RNA

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12
Q

The φ in the TφC-loop represents…

A

Pseudouridine-monophosphate

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13
Q

Describe the binding of a tRNA with an amino acid

A
  • CCA-sequence (3’-end) of tRNA

Binds to

  • Carboxyl group of amino acid
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14
Q

How are amino acids activated?

A

Binding of the adequate amino acid with the tRNA

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15
Q

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

A

Aminoacyl-tRNA-synthetase

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16
Q

Aminoacyl-tRNA-synthetase binds…

A

ATP

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17
Q

Give the reaction of amino acid binding to tRNA

A
  1. ATP + Amino acid → Aminoacyl-AMP + PPi
  2. Aminoacyl-AMP + tRNA → Aminoacyl-tRNA + AMP
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18
Q

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

A

DHU-loop

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19
Q

Give the structure of a ribosome

A
  • Proteins
  • Ribosomal RNA (rRNA)
    • Large subunit
    • Small subunit
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20
Q

Different types of rRNA can be characterised by their…

A
  • Sedimentation coefficient
  • Unit: Svedberg = S
21
Q

Give the binding sites of large ribosomal subunits

A
  • A-site
  • P-site
  • E-site
22
Q

A-binding site

A

Aminoacyl-tRNA binding site

23
Q

P-binding site

A

Peptidyl-tRNA binding site

24
Q

E-binding site

A

Exit

25
Q

Give the binding site of small ribosomal subunits

A

mRNA-binding site

26
Q

In eukaryotes, translation occurs in the…

A
  • Cytoplasm
  • RER (membrane with ribosomes)
27
Q

Summarise the steps of initiation in eukaryotes

A
  1. Pre-initiation complex
  2. Kozak-scanning mechanism
  3. Recognised start codon
  4. Initiation complex
28
Q

Give the composites of the pre-initiation complex

A
  • Small ribosomal subunit
  • eIF-2-GTP
  • other eIF-S
  • tRNAMet
29
Q

Kozak-scanning mechanism

A
  • Pre-initiation complex rolls along mRNA strand
  • Locates the start codon (AUG)
30
Q

Recognised start codon stage

A

Small ribosomal subunit binds to Kozak-sequence of mRNA

31
Q

Give the formation of the initiation complex

A
  1. Hydrolysis of the GTP bound to eIF-2 → GDP + Pi
  2. Large ribosomal subunit binds to the small
  3. All eIF-s dissociate
32
Q

What occurs at the end of initiation

A
  • Methionyl-tRNA binds via TφC-loop to P-site of the large subunit
  • A-site of the large ribosomal subunit is free
33
Q

Steps of elongation of translation in eukaryotes

A
  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
34
Q

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

A
  • 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
35
Q

Describe methionine placement onto the aminoacyl-tRNA

A
  • 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
36
Q

Translocation stage of eukaryotic translation

A
  • Dipeptidyl-tRNA placed onto the P-site
  • Catalysed by translocase
  • Requires:
    • EF-2
    • GTP complex
37
Q

Describe the end stage of eukaryotic translation

A
  • Dipeptidyl-tRNA binds to the P-site of the large RSU via TφC-loop
  • A-site of the large ribosomal subunit is free
38
Q

Describe termination of translation in pro- and eukaryotes

A
  • 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
39
Q

Initiation phase of translation in prokaryotes

A
  1. Small RSU + IF-1 and IF-3
  2. 30S initiation complex formation
  3. 70S initiation complex
40
Q

30S initiation complex is formed by

A
  • Small ribosomal subunit + IF-1 and IF-3
    • IF-2-GTP + tRNAini + mRNA
41
Q

How is the 70S initiation complex formed

A
  1. IF-1 and IF-3 dissociate
  2. GTP hydrolyses
  3. Large RSU binds
42
Q

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

A
  • 3 IF-s are needed for prokaryotes, Eukaryotes need more
  • Initiator amino acid: N-formyl-methionine in prokaryotes
  • No Kozak-scanning mechanism in prokaryotes
43
Q

Give the elongation stage of prokaryotic translation

A
  • Different elongation factors:
    • EF-Tu; EF-G
  • Transcription + translation happen simultaneously
  • One mRNA binds to more than one ribosome
    • Polyribosome
44
Q

What is shown in the figure

A

Polyribosome

45
Q

Energy requirement of: Initiation

A

1 GTP

46
Q

Energy requirement of: Kozak-scanning mechanism

A

1 ATP

47
Q

Energy requirement of: Elongation

A

4 ATP

48
Q

Energy requirement of: Termination

A

1 GTP

Biochemistry (21 decks)

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