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Biochemistry > L21 Translation > Flashcards

L21 Translation Flashcards

1
Q

In translation mRNA is used as a template for the…

A

Production of a polypeptide

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2
Q

Three 3 key characteristics of the genetic code are…

A
  1. Triplet code
  2. Non-overlapping
  3. Degenerate (redundant)
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3
Q

The genetic code is degenerate, which means one amino acid can be encoded…

A

By more than one codon

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4
Q

Different codons which code for the same amino acid are known as…

A

Synonymous codons

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5
Q

61 codons specify…

A

Amino acids

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6
Q

3 codons specify…

A

Stop

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7
Q

The stop codons are…

A

UAA, UAG, UGA

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8
Q

AUG codes for which amino acid?

A

Methionine

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9
Q

The start codon is…

A

AUG (methionine)

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10
Q

The code for amino acids:

a) varies between species
b) is almost universal
c) is universal
d) varies between prokaryotes and eukaryotes

A

b) is almost universal

There are a few exceptions, for example the stop codon in mitochondria, UGA codes for tryptophan

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11
Q

The ‘t’ in tRNA stands for…

A

Transfer

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12
Q

tRNAs form the link between…

A

RNA and protein

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13
Q

The primary structure of tRNAs (4)…

A
  1. Small (70-90nts)
  2. 15 invariant residues & 8 semi invariant residues
  3. 5’ monophosphate
  4. Modified bases (added post-transcription)
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14
Q

The modified bases in tRNA are (4)…

A
  1. Ribothymidine (T)
  2. Pseudouridine (Ψ)
  3. Dihydrouridine (D)
  4. Inosine (I) *

*important

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15
Q

The secondary structure of tRNAs (5)…

A
  1. D loop
  2. I Loop
  3. Variable arm
  4. Anti-codon loop *
  5. Amino Acid acceptor site *

*important

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16
Q

Adding amino acids to tRNA is known as the…

A

Aminoacylation of tRNA

17
Q

Aminoacylation of tRNA results in…

A

Charged (aminoacyl) tRNAs

18
Q

Aminoacylation of tRNA is a ( 1 / 2 / 3+) step reaction…

A

2

19
Q

Aminoacylation of tRNAs:

a) Does not require additional energy
b) Is driven by GTP
c) Is driven by ATP
d) Is driven by ADP

A

c) Is driven by ATP

20
Q

Aminoacylation step 1 forms a high energy intermediate known as…

A

Aminoacyl Adenylate (AMP + Amino Acid)

Two free phosphates are released from the original ATP

21
Q

In step 2 of aminoacylation, the aminoacyl adenylate reacts with…

A

A matching tRNA

This forms the aminoacyl tRNA and releases the AMP

22
Q

Amino acids are joined to either the 2’ or 3’ hydroxyls. This doesn’t matter because…

A

The two forms can freely interconvert

23
Q

Aminoacylation of tRNA involves the enzyme…

A

Aminoacyl tRNA synthetase (clases I and II)

24
Q

Aminoacyl tRNA synthetase recognises tRNAs based on their…

A

Identity elements

25
Q

What mechanism allows the aminoacyl tRNA synthetase to differentiate between similar amino acids?

A

Double-sieve mechanism

26
Q

The double-sieve mechanism involves the acylation site and the editing site, ensuring the amino acid is neither…

A

Too large or too small

27
Q

serine tRNA is written as…

A

tRNA^ser

where ‘ser’ is superscript

28
Q

serine is joined to tRNA^ser by…

A

Seryl-tRNA synthetase

29
Q

serine + tRNA^ser forms…

A

ser-tRNA^ser

also known as seryl-tRNA^ser

30
Q

The number of tRNA types is:

a) equal to the number of codons
b) more than the number of codons
c) less than the number of codons

A

c) less than the number of codons

31
Q

Some tRNAs can recognise multiple codons through…

A

Wobble base pairing

32
Q

In wobble base pairing the 5’ base on the tRNA anticodon forms…

A

Non-standard base pairs

e.g. G - U , I - A, I - C, I - U

33
Q

The difference between class I and class II aminoacyl tRNA synthetases is that they bind…

A

To different faces of tRNA

34
Q

What are the major feature of tRNA molecules and what are their functions (2)…

A
  1. Anticodon loop (allows binding to matching mRNA codons)

2. Amino acid acceptor site (binds specific amino acid)

Biochemistry (21 decks)

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