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Multiple Choice
What is the role of the A-site (aminoacyl site) in translation?
A
It is the site where incoming aminoacyl-tRNAs bind to the ribosome.
B
It is the site where tRNAs exit the ribosome after releasing their amino acid.
C
It is the site where the ribosome binds to mRNA.
D
It is the site where the growing polypeptide chain is held.
Verified step by step guidance
1
Understand the process of translation: Translation is the process by which ribosomes synthesize proteins using mRNA as a template. It involves three main sites on the ribosome: the A-site (aminoacyl site), P-site (peptidyl site), and E-site (exit site).
Focus on the A-site: The A-site is specifically responsible for binding incoming aminoacyl-tRNAs. These tRNAs carry amino acids that will be added to the growing polypeptide chain during translation.
Compare the roles of the ribosomal sites: The P-site holds the tRNA carrying the growing polypeptide chain, while the E-site is where tRNAs exit the ribosome after releasing their amino acids. The A-site is distinct because it is the entry point for new aminoacyl-tRNAs.
Eliminate incorrect options: The A-site does not hold the growing polypeptide chain (this is the P-site's role), nor is it the site where tRNAs exit (this is the E-site's role). Additionally, the ribosome binds to mRNA at a different location, not the A-site.
Conclude the correct role of the A-site: The A-site is the site where incoming aminoacyl-tRNAs bind to the ribosome, allowing the addition of amino acids to the growing polypeptide chain during translation.