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translation Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is the first step in translation?

A

amino acid activation

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2
Q

in amino acid activation, how does the amino acid get attached?

A

the attachment of an amino acid to its specific tRNA is mediated by a group of enzymes known as aminoacyl tRNA synthetases

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3
Q

how many aminoacyl tRNA synthetases are there?

A

there are 20 aminoacyl tRNA synthetases, one for each amino acid and it is able to bind all the different tRNAs that code for its specific amino acid

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4
Q

what does the aminoacyl tRNA synthetase have?

A
  • an active site, which is specific for one type of amino acid and tRNA molecule with appropriate anticodon
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5
Q

what does the enzyme do?

A

it catalyses the covalent attachment of the specific amino acid to its tRNA at the amino acid attachment site, resulting in the formation of an aminoacyl-tRNA complex

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6
Q

how is the amino acid joined?

A

by its carboxyl group to the 3’ OH of the tRNA by a ester bond. (when the tRNA has an amino acid linked to it, it is termed as “charged”

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7
Q

formation of initiator tRNAmet

A

this is used for the recognition of the start codon AUG –> in euk, initiator tRNA carried methionine

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8
Q

initiation of translation involves

A

tRNA, rRNA, mRNA and at least 10 initiation factors (proteins)

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9
Q

what happens at the initiation of translation?

A
  • the small ribo subunit binds to the 5’ end of the mRNA and a initiator tRNA, which has the anticodon UAC and carries the amino acid methionine
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10
Q

after the ribo binds?

A

the small subunit then moves downstream (5’ to 3’) along the mRNA carrying initiator tRNA until it reaches the start codon, AUG which signals the start of translation

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11
Q

after they move till the start codon?

A

the initiator tRNA then binds with the start codon through H bonding

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12
Q

large ribo subunit will bind

A

with the help of initiation factors (they are proteins)

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13
Q

after the initiation of translation occurs, it forms

A

a translation initiation complex

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14
Q

hydrolysis of GTP provides the energy for the assembly of this complex

A
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15
Q

elongation of translation

A
  • codon recognition
  • peptide bond formation
  • translocation
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16
Q

what is codon recognition (elongation)

A
  • the anticodon of an incoming aminoacyl tRNA base pairs with the complementary mRNA codon in the “A” site of the large subunit of ribosome (assisted by elongation factors)
  • requires hydrolysis of GTP
17
Q

what is peptide bond formation? (elongation)

A
  • the large ribosomal subunit catalyses a chemical reaction (destroys the covalent bond) that releases methionine from the initiator tRNA at the “P” site and attaches it instead by a peptide bond to the second amino acid which is attached to the aminoacyl-tRNA at the “A” site
18
Q

what enzyme is inside the large ribo subunit?

A

peptidyl transferase!! and it catalyses the peptide bond formation as well as the breakdown of the covalent bond

19
Q

what is translocation (elongation)

A
  • it translocated three more nucleotides along the mRNA molecule/one codon in the 5’ to 3’ direction
  • hydrolysis of GTP provides energy for this step

it relocates everything one down!!!

20
Q

after translocation?

A

at “A” site –> it receives another aminoacyl-tRNA which has an anticodon complementary to the third codon of the mRNA
- then REPEAT

21
Q

how to terminate after mRNA is translated?

A
  • continues until a stop codon in the mRNA reaches the “A” site
  • a release factor binds directly to the stop codon in the “A” site (does not code for any amino acid)
  • this causes the addition of a water molecule instead of an amino acid to the polypeptide chain, hydrolysing the polypeptide chain from the tRNA in the P site
22
Q

the polypeptide is then formed then

A

it is then released from the ribosome and then it disassembles into its subunits

23
Q

what is the stop codon

A

uag uaa uga

Biology (10 decks)

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