Question

which of the following occurs at the p site in the picture above?
the mrna enters the ribosome
the mrna exits the ribosome
the peptide chain elongates
nothing

Explanation:

In protein synthesis, the ribosome has three sites: A (aminoacyl), P (peptidyl), and E (exit). The P - site holds the tRNA with the growing peptide chain. During elongation, the peptide chain is transferred from the tRNA at the P - site to the amino acid - charged tRNA at the A - site, thus elongating the peptide chain. The mRNA enters the ribosome in a general sense for the process but not specifically at the P - site. The mRNA does not exit at the P - site (it exits in a different context, but not as a function of the P - site's main role). And "nothing" is incorrect as the P - site is actively involved in peptide chain elongation.

Answer:

The peptide chain elongates