Final answer:
tRNA molecules carry amino acids to the ribosome where each amino acid is covalently bonded to a growing polypeptide chain through a peptide bond, facilitated by peptidyl transferase.
Step-by-step explanation:
The tRNA molecules deliver amino acids to ribosomes where the amino acid next is covalently bonded to a growing polypeptide through a peptide bond. This crucial step in protein synthesis is catalyzed by the enzyme peptidyl transferase, which is a component of the ribosome. The bond that is formed is between the carboxyl group of the amino acid that is already part of the chain (on the tRNA occupying the P-site) and the amino group of the new amino acid brought to the A-site by its corresponding tRNA.
Each tRNA molecule has a specific anticodon that matches the codon on the mRNA. For instance, a tRNA that shuttles lysine recognizes the mRNA codon AAG with its anticodon UUC. When the correct tRNA docks onto the mRNA codon at the ribosome, the amino acid it carries is positioned to be added to the growing peptide chain.
After the new amino acid is covalently attached to the polypeptide, the tRNA is then released from the ribosome and can be recycled to attach to another amino acid and repeat the process. The sequence of amino acids in the polypeptide chain continues to grow as more tRNAs bring in their respective amino acids and the ribosome moves along the mRNA strand reading the codons until it reaches a stop codon, at which point the completed polypeptide chain is released.