Question

Which of the following statements is false about viruses?

• A. Viruses are obligate parasites.
• B. Viruses can multiply only when they are inside the living cells.
• C. Viruses cannot pass bacterial proof filters.
• D. Viruses are made up of protein and DNA or RNA.

Hint:

Remember the keyword “filterable agents”. Viruses are much smaller than bacteria and can pass through bacterial proof filters. This property played a crucial role in their discovery.

Answer 1

The Correct Option is C

Concept: Viruses are extremely small, acellular infectious particles that lie at the boundary between living and non-living organisms. They do not possess a cellular organization and cannot perform metabolic activities independently. Therefore, they depend completely on a living host cell for their multiplication. A virus consists mainly of:
• A nucleic acid core (either DNA or RNA)
• A protein coat called capsid One important historical characteristic of viruses is that they are filterable agents. They can pass through special filters that retain bacteria. This property led to their discovery.

Step 1: Examine Option (A)
The statement says: \[ \text{Viruses are obligate parasites} \] An obligate parasite is an organism that can survive and reproduce only within a living host. Viruses lack:
• Ribosomes
• Cytoplasm
• Independent metabolic machinery
• Energy-generating systems Therefore, they must utilize the machinery of a host cell for replication. Hence, this statement is true.

Step 2: Examine Option (B)
The statement says: \[ \text{Viruses can multiply only when they are inside living cells} \] Outside the host cell, viruses remain metabolically inactive and exist in the form of virions. Replication begins only after:
• Attachment to the host cell
• Entry into the host
• Utilization of host cellular machinery Therefore, multiplication occurs only inside living cells. Hence, this statement is also true.

Step 3: Examine Option (C)
The statement says: \[ \text{Viruses cannot pass bacterial proof filters} \] This statement contradicts one of the most important properties of viruses. Viruses are much smaller than bacteria and can easily pass through bacterial proof filters such as Chamberland filters, which trap bacteria. Historically, viruses were discovered because infectious agents could pass through these filters even after bacteria had been removed. Therefore, \[ \text{Viruses CAN pass bacterial proof filters.} \] Hence, this statement is false.

Step 4: Examine Option (D)
The statement says: \[ \text{Viruses are made up of protein and DNA or RNA} \] A virus contains:
• Protein coat (capsid)
• Genetic material (DNA or RNA) A virus never contains both DNA and RNA simultaneously as genetic material. The statement correctly conveys that viruses contain protein and either DNA or RNA. Hence, this statement is true. Final Conclusion: Among the given statements, only Option (C) is incorrect because viruses are capable of passing through bacterial proof filters. Hence, \[ \boxed{\text{Correct Answer}=(C)} \]