Topic 13.3: Translation Flashcards

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1
Q

how many rRNA and protiens do prokaryotes and eukaryotes have

A

prokaryotes - 3 rRNA and many proteins

eukaryotes - 4 rRNA and many proteins

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2
Q

what subunits of ribosome are there in prokayrotes and eukaryotes

A

prokaryotes - 30S + 50S subunits = 70S ribosome

eukaryotes - 40S + 60S subunits = 80S ribosome

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3
Q

what is required for translation

A
adaptor molecule = tRNA
template = mRNA
enzyme = rRNA in ribsomes
substrates = activated amino acids
SO tRNA with activated amino acids
initiation factors, elongation factors, release factors, and energy (GTP/ATP)
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4
Q

what are some key features of genetic code

A

triplet code - 3 base pairs = amino acid
degenerate = more than one triplet code (codon) for same amino acid
non overlapping and ‘comma less’ - no gaps

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5
Q

what is a key feature of translation

A

5 to 3 prime end template read through to produce N to C polypeptide chain extension

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6
Q

what is the initiation codon

A

AUG

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7
Q

what is the termination codon

A

UAA, UAG, UGA

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8
Q

whjat is the role of tRNA

A

each tRNA can bind an amino acid to its 3 prime end (as it can be charged with an activated amino acid)
each tRNA has an anticodon to recognise a complementary codon in mRNA

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9
Q

how do tRNA become charged and attached to activated amino acids

A

Aminoacyl-tRNA synthetase will recognize a specific amino acid and then binds to ATP to charge amino acid
the same enzyme will then recognize a specific tRNA using anticodon and binds specific amino acid to specific tRNA to form a charged tRNA with aminoa cid attached

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10
Q

what happens during initiation of translation

A

mature mRNA has 5 prime CAP and initiation codon (AUG)

  1. the cap is recognized by cap binding proteins, which along with initiation factors, small ribosome and energy, the tRNA-methionine (amino acid activated) become attached
  2. the complex moves across mRNA until it reaches AUG which is recognized by the anticodon on P site of tRNA-amino acid complex (needs energy)
  3. initiation factors are lost and a large subunit is being recruited (functional ribsoome subunit ready). so results in tRNA-methionine complex bound to AUG initiation codon and a functional ribosome assembled
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11
Q

what results from initiation

A

80s initiation complex with tRNA-methionine in P site of ribosome on AUG on mRNA and empty A site on ribosome ready for elongation

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12
Q

what are the sites called on functional ribosome

A

E, P, A from 5 to 3 prime end

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13
Q

why is the A site empty

A

to receive the next tRNA-amino acids complex

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14
Q

what happens during elongation of translation

A
  1. the next codon can be recognized at empty A site where binding of aminoacyl-tRNA occurs with its cognate amino acid attached to it (GTP required)
  2. peptide bond formation occurs catalysed by peptidyltransferase between first amino acid and second one and the first one is thus a uncharged tRNA which is in E site
  3. translocation occurs - ribosome moves across mRNA (need GTP), one codon at a time from 5 to 3 end.
  4. the peptidy- tRNA complex moved to P site and empty A site forms so new codon is being freed, the growing polypeptide is ‘pushed’ intp exit tunnel, elongation factors are involved
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15
Q

what results from elongation

A

peptidyl-tRNA in P site and empty A site ready for next cycle
only 2 sites occupied of EPA

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16
Q

what happens in termination

A

stop codon is recognise on mRNA by release factor and one water molecule is brought into ribosome which causes a hydrolysis reaction and the tRNA molecules becomes uncharged in P site and the peptide is free and exits in tunnel. the ribosomes then become dissociated into subunits

17
Q

What are the function of release factors

A

Release factors promote polypeptide chain termination

18
Q

What is translation

A

Ribosomes polymerise amino acids to form proteins

19
Q

Best chronological gene expression order

A
Promoter recognition
mRNA synthesis
Splicing
Methiontl-tRNA synthetase catalysed reaction
Recruitment of 60S subunit to form 80S initiation complex
Translocation
Ribosome dissociation
Protein folds into final 3D structure