Point 20 of 25 — Lesson 1: Types of RNA, Genetic Code and Protein TranslationQuestion bank: 14 questions (14 with pictures)
20Elongation
The ribosome has two main tRNA-binding sites: thepeptidyl (P) siteand theaminoacyl (A) site.
After initiation, AUG with its tRNA is at the P site, and the codon for the second amino acid is lined up at the A site.
The chain then lengthens by repeating a three-step cycle:
Binding: the tRNA whose anticodon matches the next codon enters the A site, bringing the next amino acid.
Peptide-bond formation:peptidyl transferase, an integral part of the large ribosomal subunit, joins the first amino acid to the second with a peptide bond; the first tRNA is now empty, and the tRNA at the A site holds the two amino acids.
Translocation:the ribosomemoves along the mRNA by one codon. The next codon enters the A site, and the cycle repeats; the growing polypeptide is always attached to the tRNA that arrived most recently.
📝 Question bank for this point
14 questions linked to this point only, 14 of them with pictures.
