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BIOCHEMISTRY > Mechanisms of Protein synthesis > Flashcards

Mechanisms of Protein synthesis Flashcards

1
Q

Where does ribosome attach to on mRNA

A

5’ end where protein syn. occurs

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2
Q

Where does amino acid attach to tRNA

A

3’ ACC end of tRNA= amino acyl-tRNA

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3
Q

What does anticodon on tRNA act as?

A

Recognition site for codons on mRNA

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4
Q

What is formation of amino acyl tRNA catalysed by?

A

amino acylt-tRNA synthetase - proof reads

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5
Q

What is degeneration within Code of bases?

A

1 or more Codon encode same amino acids

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6
Q

How many possible amino acid triplets?

A

64

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7
Q

What does degeneration within code minimise?

A

Harmful effects

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8
Q

What are unambigious codons?

A

Met and Try for start and stop codons

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9
Q

What is Purine rich section on mRNA?

A

Shine Dalgarno sequence

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10
Q

What does shine Dalgarno sequence do?

A

forms complementary base pairing with 16s rRNA protein part of 30s ribosome subunit

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11
Q

What signal initiates translation at AUG codon?

A

fMet start signal - tRNA with Methionine amino acid

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12
Q

Do mitochondria contain ribosomes and DNA ?

A

Yes

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13
Q

Does mitochondria have their own genome?

A

Yes because they’re free living bacteria

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14
Q

Where is new amino acids added onto growing peptide chain in protein synthesis?

A

Carboxyl end

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15
Q

What does organisms adopt to increase efficient protein synthesis?

A

adopt error rate frequency of 10*-4

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16
Q

What is found in tRNA?

A

Methylated or demethylated versions of A U C G

17
Q

How is L shaped of tRNA formed?

A

4 helices of secondary structure stacked

18
Q

What does flexible CCA amino attachment site do?

A

flexible so move amio acid between editing and activation site

19
Q

What are ribosomes in Prokaryotes?

A

70s - made from 30s small and 50s large units

20
Q

What are ribosomes in Eukaryotes?

A

80s - made from 40s small and 60s large

21
Q

What brings 2 subunits of 70s Ribosome together?

A

mRNA

22
Q

What is a group of ribosomes bound to an mRNA ?

A

Polysome

23
Q

What does the Purine rich Shine Dalgarno site allow?

A

Binding of mRNA to ribosome

24
Q

How is there 3 tRNA binding sites within 50S subunit?

A

bridge gap between 50s and 30s

25
Q

What does A & P tRNA binding site of 50s Subunit bind to?

A

mRNA

26
Q

What is the mRNA bound to?

A

30S subunit

27
Q

What is the Protein Synthesis Mechanism?

A

1) 1st tRNA bind to A site and peptide forms with Methionine amino acid
2) ribosome moves to the right so original tRNA in the A site moves to P site
3) A site open for next Amino tRNA

28
Q

What happens at P site?

A

Where polypeptide chain formed

29
Q

What happens at E site?

A

where tRNA without amino acid exits

30
Q

What is always the first amino acid to be added to polypeptide chain?

A

Methionine

31
Q

What is translocation driven by?q

A

Elongation factor G ( Enzyme)

32
Q

What directs fMet tRNA to p Site?

A

initiation factor 1

33
Q

where does IF1 AND IF3 bind to?

A

30S subunit

34
Q

What does IF3 do?

A

prevent premature 30s and 50s binding w/o any mRNA or fMet-tRNA

35
Q

What does Elongation factor Tu do?

A

catalyse binding of amio acyl-tRNA to A site of 50S

36
Q

What does IF2 do?

A

binds GTP protein to fMet-tRNA

37
Q

How is polypeptide chain in 50S ribosome deposited?

A

via a Tunnel

38
Q

How is tRNA modified to mature mRNA?

A
  • cleavage of 5’ leading sequence
  • splicing to remove intron
  • replacement of 3’ terminal UU to CCA
  • Modifies several bases
  • anticodon formed
39
Q

What is the wobble hypothesis?

A

tRNA molecules to recognize more than 1 codon due to degeneracy

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