Relate the structure of bacteriophages and animal viruses to the structure of their respective host cells and the steps of the viral life cycle

Question

What will be an ideal response?

Answer 1

Answer: The T4 phage has a very complex structure, containing a head, collar, tail, tail pins, an endplate, and tail fibers. The tail fibers bind to specific receptors on the surface of a bacterial cell (outside the peptidoglycan cell wall). When the tail fibers retract, the tail pins bind to the host so that the tail itself interacts with the cell wall. A viral enzyme then forms a small pore in the host cell wall. The tail's covering then contracts and inserts the virus into the host's cytoplasm. Animal viruses are usually much simpler in structure than bacteriophages because animal host cells lack a cell wall. Penetration is therefore somewhat easier and is usually accomplished by endocytosis or merging of the viral envelope with the host cell membrane. The complicated fibers and contractile tail are not needed to penetrate the animal cell. One last difference is that the entire virion often enters the animal cell and not just the viral genome.