Which term best describes a microorganism that can only reproduce by invading living cells?

Which term best describes a microorganism that can only reproduce by invading living cells?

• A. Bacteria
• B. Virus
• C. Fungi
• D. Protozoa

Answer: (B)

A virus is defined by its dependence on living cells to reproduce. It cannot make copies of itself on its own because it lacks the cellular machinery—like ribosomes, enzymes, and energy sources—that cells use to copy genetic material and build proteins. Instead, a virus must invade a host cell and hijack that cell’s machinery to produce viral components, assemble new viruses, and release them to infect more cells. Outside a living cell, viruses are inert and do not multiply. Bacteria, fungi, and protozoa are cellular organisms that can reproduce independently under suitable conditions, using their own cellular processes. They don’t rely on a host cell to replicate in the same way viruses do. This distinction underpins infection control: to prevent transmission, strategies focus on inactivating or removing viruses from surfaces and instruments, since viruses depend on host cells to reproduce and spread.

A virus is defined by its dependence on living cells to reproduce. It cannot make copies of itself on its own because it lacks the cellular machinery—like ribosomes, enzymes, and energy sources—that cells use to copy genetic material and build proteins. Instead, a virus must invade a host cell and hijack that cell’s machinery to produce viral components, assemble new viruses, and release them to infect more cells. Outside a living cell, viruses are inert and do not multiply.

Bacteria, fungi, and protozoa are cellular organisms that can reproduce independently under suitable conditions, using their own cellular processes. They don’t rely on a host cell to replicate in the same way viruses do.

This distinction underpins infection control: to prevent transmission, strategies focus on inactivating or removing viruses from surfaces and instruments, since viruses depend on host cells to reproduce and spread.