tRNA is a kind of ribonucleic acid that has a role in transporting a specific amino acid (AA) to the ribosome.The ribosome is protein/RNA complex that has a big role in protein translation. It is composed of three major sites: P, A and E site.When the tRNA-AA complex arrives in the ribosome, it always goes to the A site (except for the first one which goes directly to the P site) since the P site is supposed to handle a tRNA carrying a polypeptide.Then a reaction occurs between the amino acid in the A site and the polypeptide to form a peptidic bound between them.After that, the ribosome will translocate to the next codon in the mRNA, The tRNA in A site will be translocated to P site. tRNA in the P site of the ribosome will enter the E site. The polypeptide sequence stays in the P site. and another tRNA-AA complex arrive in the A site to start the next cycle.
