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Multiple Choice
Shown below is a ribosome in the process of translation. The P site of a ribosome __________.
A
is where the mRNA first binds to the ribosome
B
binds the tRNA carrying the next amino acid to be added
C
is the site where the release factor binds during termination
D
holds the tRNA carrying the growing polypeptide chain
Verified step by step guidance
1
Understand the structure and function of a ribosome: A ribosome has three main sites involved in translation - the A site (aminoacyl site), P site (peptidyl site), and E site (exit site). These sites play distinct roles in the process of protein synthesis.
Recall the role of the P site: The P site is specifically responsible for holding the tRNA that carries the growing polypeptide chain during translation. This is where the peptide bond forms between the growing chain and the new amino acid.
Differentiate the roles of the ribosomal sites: The A site binds the tRNA carrying the next amino acid to be added to the chain, the P site holds the tRNA with the growing polypeptide chain, and the E site is where the tRNA exits the ribosome after its amino acid has been added.
Eliminate incorrect options: The P site does not bind mRNA (this occurs at the ribosome's small subunit), it does not bind the tRNA carrying the next amino acid (this is the A site's role), and it is not the site where the release factor binds during termination (this occurs at the A site).
Conclude that the correct answer is: The P site holds the tRNA carrying the growing polypeptide chain, as this is its primary function during translation.