Final answer:
The fifth step of protein synthesis is post-translational modification, where the new protein is processed and modified to become functional.
Step-by-step explanation:
The fifth and last step of protein synthesis is known as post-translational modification. This step occurs after the initial synthesis of the polypeptide chain on the ribosome. The process includes various changes that a new protein undergoes to become fully functional. Such changes can include folding into its proper three-dimensional shape, forming disulfide bridges, being cut into smaller pieces,
having certain amino acids modified, or other modifications like being tagged for transport to specific areas of the cell. This step is crucial for the realization of the final, functional form of the protein, which can then go on to perform its role in the cell.