NEET BIOLOGY

Detailed explanation-1: -To infect a cell, it is critical that a virus initiates attachment-the binding of the virus to the host cell. This interaction is specific: the virus contains a virus attachment protein that adsorbs to a cell surface receptor on the cell (Table 4.1 ).

Detailed explanation-2: -Virus entry into animal cells is initiated by attachment to receptors and is followed by important conformational changes of viral proteins, penetration through (non-enveloped viruses) or fusion with (enveloped viruses) cellular membranes. The process ends with transfer of viral genomes inside host cells.

Detailed explanation-3: -Viruses initially stick to cell membranes through interactions unrelated to fusion proteins. The virus surfs along the fluid surface of the cell and eventually the viral fusion proteins bind to receptor molecules on the cell membrane (4).

Detailed explanation-4: -The first stage is entry. Entry involves attachment, in which a virus particle encounters the host cell and attaches to the cell surface, penetration, in which a virus particle reaches the cytoplasm, and uncoating, in which the virus sheds its capsid.

Detailed explanation-5: -The viral attachment protein can be viewed as the “key” that unlocks host cells by interacting with the “lock”-the receptor-on the cell surface, and these lock-and-key interactions are critical for viruses to successfully invade host cells.