Week 6_details of translation

Question 1

what are the phases of translation?

Answer 1

initiation

elongation

termination

Question 2

what occurs during initiation in translation?

Answer 2

assembly of ribosome/mRNA/charged tRNAs

Question 3

what occurs during elongation in translation?

Answer 3

starts at the ‘Start’ codon (methionine)

amino acids are added until the ‘Stop’ codon

Question 4

what occurs during termination in translation?

Answer 4

new protein is released from the ribosome

ribosome complex disassembles

Question 5

what are the steps of initiation in prokaryotes?

Answer 5

(1) rRNA in small ribosomal subunit binds the mRNA at the 5’ ribosome binding sequence (complementary rRNA/mRNA sequences)

(2) initiator tRNA binds to the start codon (AUG) (methionine)

(3) large ribosomal subunit joins and initiation is complete

Question 6

what are the steps of initiation in eukaryotes?

Answer 6

(1) small ribosomal subunit + initiator Met tRNA bind to the mRNA 5’ cap

(2) complex scans the mRNA until it finds the start codon (AUG)

(3) large ribosomal subunit joins the complex and initiation is complete

Question 7

what are the binding sites on the ribosome tRNA?

Answer 7

E –> where uncharged tRNAs are ejected

P –> where initiator tRNA binds

A –> where the next tRNA binds carrying the next amino acid to be added to the protein

Question 8

what is translocation?

Answer 8

the movement of the ribosome down the length of the mRNA

Question 9

proteins are always synthesized in the ___ direction

Answer 9

N-terminal –> C-terminal

Question 10

what are the steps of translation termination?

Answer 10

(1) release factor is a protein that binds to the stop codon (no tRNAs for the stop codons)

(2) protein is released from the ribosome

(3) ribosome complex falls apart

Question 11

what are the steps in elongation?

Answer 11

initiation complete: the initiator tRNA is bound to the P site:
(1) a new charged tRNA binds to the A site

formation of the peptide bond:
(2) amino acid chain is transferred from the tRNA in the P site to the tRNA in the A site
- the tRNA in the P site now has no AA (uncharged)

translocation:
(3) ribosome moves 1 codon down the mRNA
- uncharged tRNA in the P site shifts to the E site (ejected)
- tRNA in the A site shifts to the P site
- a new charged tRNA can now bind to the codon in the A site