The answer is P-site. Ribosomes are composed of two subunits, one
small and one large. Four binding sites are located on the ribosome, one for
mRNA and three for tRNA. The three tRNA sites are labeled P, A, and E. The A
site (acceptor site), binds to the aminoacyl tRNA, which holds the new amino
acid to be added to the polypeptide chain.
Endocytosis can be defined as the process by which foreign components or molecules present in the external environment or exterior of the cell are transferred to the cell interior.
This happens by the invagination of the plasma membrane of the cell towards the cell interior forming an incomplete vesicle-like structure.
The foreign components or molecules localize inside this vesicle-like structure.
This structure then buds or pinches off inside the cell forming a complete vesicle containing the foreign components or molecules.
When the non-enveloped animal virus adsorbs to the surface of the host animal cell with its protein spikes, it signals the plasma membrane of the cell to undergo the process of invagination or endocytosis. Hence, by this way the virions are internalized into the cell.
The seminal vesicle and the prostate glands add their secretions so that the sperm are in a fluid that makes their transport easier, and this fluid also provides nutrition.
