What do act like what because they destroy cells in which multiply?

Viruses destroy cells in which they multiply because they are obligate intracellular parasites. This means that they require a living host cell to replicate and cannot survive outside of a host cell. When a virus enters a host cell, it hijacks the cell's machinery to produce more copies of itself. This process can damage the host cell and eventually lead to its death.

Viruses have a variety of mechanisms to destroy host cells. Some viruses produce proteins that directly kill the host cell. Other viruses damage the host cell's DNA or RNA, leading to cell death. Still other viruses cause the host cell to undergo apoptosis, a form of programmed cell death.

The type of damage that a virus causes depends on the virus itself and the host cell that it infects. Some viruses are very destructive and can cause severe disease, while others are relatively harmless.

Here are some examples of how viruses can destroy cells:

* The influenza virus produces a protein called hemagglutinin that binds to receptors on the surface of respiratory cells. This binding allows the virus to enter the cell, where it replicates and eventually destroys the cell.

* The human immunodeficiency virus (HIV) infects white blood cells called CD4+ T cells. HIV damages the DNA of these cells, leading to cell death. This can eventually lead to AIDS, a life-threatening condition.

* The Ebola virus causes a hemorrhagic fever that is characterized by severe bleeding and tissue damage. The virus damages the endothelial cells that line the blood vessels, leading to leakage of blood and tissue damage.

Viruses are a major cause of disease in humans and animals. The development of vaccines and antiviral drugs has helped to reduce the impact of viral diseases, but there is still much that we do not know about how viruses work.