Final answer:
After translation, proteins undergo post-translational modification, such as folding, chemical modification, and signal sequence addition, before they can be considered entirely 'finished' and functionally active.
Step-by-step explanation:
After translation, a protein is not immediately 'finished' as it undergoes several steps of post-translational modification, which are crucial for it to become biologically active. The process begins with the termination of translation, where a stop codon (UAA, UAG, or UGA) on the mRNA leads to the release of the newly synthesized polypeptide chain from the ribosome. Following this, the protein may need to be folded into its three-dimensional structure, have certain amino acids chemically modified, or have signal sequences appended. These modifications can include the removal of the N-terminal methionine, the addition of carbohydrates, phosphates, or lipids, and the cleaving of signal peptides. Additionally, proteins may be directed to specific cellular compartments if they have a signal sequence — akin to a 'train ticket' guiding them to the correct destination like the mitochondria or chloroplasts. Once at the proper location, the signal sequence is generally removed, and the protein becomes fully functional.