What physiological process is primarily mediated by endosomes during viral infection?

• A. Viral replication
• B. Endocytosis
• C. RNA synthesis
• D. Protein degradation

Answer: (B)

Endosomes play a crucial role in the process of endocytosis, which is essential during viral infections. When a virus enters a host cell, it often does so by binding to specific receptors on the cell’s surface. This interaction triggers the process of endocytosis, where the cell membrane engulfs the virus and forms an endosome that contains the viral particles.

Once inside the endosome, the acidic environment can lead to changes in the viral envelope or the viral particle itself, triggering the release of the viral genome into the cytoplasm or enabling the virus to fuse with cellular membranes. This step is vital for the virus to effectively hijack the host's cellular machinery for replication and propagation.

While viral replication, RNA synthesis, and protein degradation are important in the lifecycle of a virus, these processes occur after the endosome-mediated entry has taken place. Therefore, the primary role of endosomes in the context of viral infection is to facilitate the entry of the virus into the host cell through endocytosis.