Module 3 Translation, Elongation and Termination for E. Coli

Question 1

Translation, Elongation and Termination for E. Coli:

The 50S ribosomal subunit of E coli consists of 3 things:

1) that binds incoming tRNAs

2) binds charged tRNAs carrying amino acids that have formed peptide bonds with the growing polypeptide chain but not have dissociated.

3) releases dissociated tRNAs so they can be recharged with new amino acids.

Answer 1

1) A Aminoacyl site

2) P Peptidyl site

3) E Exit site

Question 2

tRNAs that can by-pass the A Aminoacyl site

Eukaryotes:

Prokaryotes:

They both free up the A site to accept the tRNA after the start codon

Answer 2

Eukaryotes:
fMet - tRNAMetf

Prokaryotes:
Met-tRNA

Question 3

Translation, Elongation and Termination for E. Coli:

___ proceeds with charged tRNAs entering the A site and then shifting to the P sites followed by the E site.

Answer 3

Elongation

Question 4

In every step of Elongation:

The energy is provided by a ____ that ____

Through the ___ the ____ then form between the amino group of the amino acid attached to the A-site-tRNA and the _____ of the Amino acid attached to the P-site tRNA

After the amino-acid in P-site is linked, it enters the E site which then the previous tRNA detaches from the amino acid

Answer 4

Elongation Factor
Hyrdrolyzes GTP

Peptidyl transferase
Peptide bond (A-site tRNA)

Carboxyl group (P-site tRNA)

Question 5

E.Coli Elongation:

The _____ takes only ___ seconds to add each amino acid

200 amino acids can be added in 10 seconds

Answer 5

E.Coli translation apparatus

0/05

Question 6

____ occurs when a ____ codon (UAA, UAG or UGA) is encountered.

This is recognized by the ___. They then instruct ____ to add a water molecule to the ___ of the P-site amino acid which causes the detachment.

Answer 6

Termination of translation

Nonsense codon

release factors
peptidyl transferase
carboxyl end

Question 7

Summary:

Initiation:

Elongation:

Termination:

Answer 7

Initiation:
Ribosome binds mRNA at start codon

Elongation:
Polypeptide chain elongates by successively adding amino acids

Termination:
When a stop codon is encountered, polypeptide is release and ribosome dissociates.

Question 8

Elongation factor purposes (3)

Answer 8

Codon recognition

Peptide bond formation

Translocation

Question 9

Large ribosomal unit contains: (3)

Small ribosomal unit contains:

Answer 9

Large ribosomal unit contains: (3)
E-site (Exit site)
P-site (Peptidyl site)
A-site (aminoacyl site)
Small ribosomal unit contains:
mRNA-binding site

Question 10

The elongation cycle of translation - overview

1. ____ An incoming aminoacyl tRNA binds to the codon in A site
2. ____ Ribosome catalyzes the formation of a peptide bond between the new amino acid and the carboxyl end of the growing polypeptide
3. ____ The tRNA in A site is translocated to the P site. Then the previous tRNA which was in the P site is moved to the E site where it is released.

Answer 10

Codon recognition

Peptide Bond Formation

Translocation