Question

Which of the following viral types enter animal cells via fusion with the animal cell membrane?

Multiple Choice

• enveloped viruses

• non enveloped viruses

• naked viruses

• All of these choices are correct.

Answer 1

Viruses are infectious agents that infects and replicate inside a host cell. They enter the host cell and hijacks its cellular and metabolic machinery and program them to produce several copies of the virus. Viruses contains a genetic material (DNA or RNA), a protein coat that surrounds it and an outermost envelope in some enveloped viruses.This envelope is derived from the host cell membrane alongwith some viral proteins. Non enveloped viruses lack this lipid envelope and is surrounded by the proteinaceous coat only.

For entry into the host cell, enveloped viruses attaches to host cells by mediated by binding between viral envelope proteins and specific host cell surface receptors. This brings the viral membrane and host cell membrane in close proximity followed by fusion of both the membranes and the viral contents are released into the host cell. Other mechanisms for entry of enveloped viruses includes receptor mediated endocytosis,

Non enveloped viruses on the other hand enter host cells by penetration of cell membrane and endocytic mechanisms. Naked viruses on the other hand utilizes endocytic pathways to enter the host cell. Therefore, only enveloped viruses enter host cells by membrane fusion.