Chapter 14.6.3 (Exam 3) Three Steps Flashcards
The Coding Sequence in mRNA Is Translated into Proteins by Ribosomes
What is initiation in translation?
Formation of initiation complex
What is the initiation complex?
Initiation complex = Charged tRNA + small ribosomal subunit + mRNA
Where on mRNA does the small ribosomal subunit (rRNA) bind?
Shine—Dalgarno sequence in prokaryotes
5’ G-Cap in eukaryotes
What amino acid does the first tRNA carry?
Methionine - A tRNA charged with methionine (anticodon UAC)
The large subunit joins the complex; the charged tRNA is now in the P site
The A site is aligned with the second mRNA codon
What happens during elongation during translation?
Another charged tRNA enters A site; the large subunit catalyzes two reactions:
The bond between tRNA in P site and its amino acid is broken
A peptide bond forms between that amino acid and the amino acid on tRNA in the A site
What is the enzyme responsible for catalyzing the two reactions in the large subunit in a ribosome?
Peptidyl transferase
What happens to the first tRNA after it releases methionine?
It moves to the E site and dissociates from the ribosome
Describe termination during translation.
Translation ends when a stop codon enters the A site
A protein releasee factor hydrolyzes the bond between the polypeptide and the tRNA in the P site
The polypeptide then separates from the ribosome
What is the role of a polyribosome/polysome?
A strand of mRNA with associated ribosomes is called a polyribosome, or polysome
When a single mRNA strand is being translated by multiple ribosomes at once, many copies of a polypeptide can be made at the same time
