Final answer:
Glycosylation of proteins occurs in the Golgi apparatus after their synthesis on ribosomes. The Golgi apparatus works together with the endoplasmic reticulum and vesicles for protein modification and distribution.
Step-by-step explanation:
The process of adding sugar groups to proteins is known as glycosylation. This modification occurs in the Golgi apparatus after the initial synthesis of the protein on the ribosome. The proteins are then packaged into the endoplasmic reticulum, where they may undergo further modifications before being tagged in vesicles, which transport the glycoproteins to their final destinations. In contrast to glycosylation, the RNA components of ribosomes are synthesized in the nucleolus, an organelle found within the nucleus of eukaryotic cells.
Once synthesized on free ribosomes in the cytoplasm, proteins may still interact with the Golgi apparatus if they need to be secreted or inserted into cellular membranes. The endoplasmic reticulum and the Golgi apparatus are also integral parts of the cellular machinery regarding protein processing and trafficking. Together with vesicles, they orchestrate the correct folding, modification, and transport of proteins throughout the cell.