Chapter 2 2.5 – Cell wars

Cell wars A disease is any condition that is harmful to or interferes with the well-being of an organism

The invaders Many diseases are caused by agents that invade the body and interfere with the normal activities of cells The invasion is called an infection Some of the invaders are living things Ex: bacteria, fungi, or parasitic worms These invaders either rob cells of their nutrients or produce waste products that poison cells

Bacteria Many bacteria are helpful but some cause disease and harmful effects Tetanus, strep throat, and pneumonia are a few common diseases Bacteria are also responsible for spoiling food and contaminating drinking water

Fungi Fungi cause several human diseases Most of these diseases are just annoying Ex: Athlete’s foot Very few of them can be deadly

protists Malaria is caused by an animal-like protist called Plasmodium It is transmitted by infected female mosquitoes Malaria is widespread in tropical countries

Viruses Viruses are often grouped with living invaders However, they are not living because they are not true cells A virus contains no nucleus, cytoplasm, organelles, or cell membrane It is a small strand of genetic information covered by a protein coat

viruses Viruses are only active once they invade a living cell They take over the cell and turn it into a factory for making more viruses Viruses are responsible for many diseases Ex: colds, cold sores, influenza, and HIV/AIDS

viruses