Which of the following statements concerning viruses is true?
View Available Hint(s)
Viruses possess enzymes for protein synthesis and ATP generation.
Viruses are usually about the same size as bacteria.
Viruses contain both DNA and RNA, and they undergo binary fusion.
The “host range” for a virus is determined by the presence or absence of particular components on the surface of a host cell that are required for the virus to attach.
The correct answer and explanation is :
Correct Answer:
The “host range” for a virus is determined by the presence or absence of particular components on the surface of a host cell that are required for the virus to attach.
Explanation (300+ words):
Viruses are unique infectious agents that differ significantly from bacteria and other microorganisms. Unlike living cells, viruses are acellular and lack the machinery necessary for independent life. One of the most important characteristics of a virus is its host specificity, which refers to the range of host cells it can infect. This is determined by the “host range,” and it is controlled primarily by the interaction between viral surface proteins and specific receptor molecules on the surface of potential host cells.
Viruses attach to host cells using specialized structures such as spike proteins or other surface molecules. These structures must fit precisely with receptors on the host cell’s surface, much like a key fits into a specific lock. If the host cell does not have the correct receptor, the virus cannot attach and infect that cell. This is why some viruses only infect certain species, tissues, or even specific types of cells within an organism.
Let’s analyze the incorrect choices:
- “Viruses possess enzymes for protein synthesis and ATP generation”: False. Viruses do not carry the necessary cellular machinery like ribosomes for protein synthesis or mitochondria for ATP production. They rely entirely on the host cell to carry out these functions.
- “Viruses are usually about the same size as bacteria”: False. Viruses are much smaller than bacteria. While bacteria typically range from 1 to 10 micrometers, viruses are usually between 20 to 300 nanometers—making them visible only under electron microscopes.
- “Viruses contain both DNA and RNA, and they undergo binary fission”: False. Viruses contain either DNA or RNA, never both. Additionally, they do not reproduce by binary fission (which is how bacteria divide). Instead, viruses replicate by hijacking the host cell’s machinery.
In summary, the statement about the “host range” being determined by the presence of specific cell surface components is correct and highlights a crucial aspect of viral infection and specificity.