Basics of Biology

Microorganisms: * Small living organisms; there are 3 types * Bacteria – ecoli, salmonella * Fungi – mushrooms, athletes foot * Virus – influenza (flu), HIV * When they enter our body, they multiply and release toxins / harmful chemicals into our blood * They duplicate every 20 minutes * Physical barriers: eyelashes prevent MO’s from entering through our eyes, nasal hairs reduce them, skin is a barrier to them (although they can enter through cuts), chemicals in tears and sweat, acid in the stomach kills most MO’s * Also called pathogens (microorganisms that cause disease) * Our body provides MO’s with ideal conditions to multiply in (warm and moist)
The immune system: * All white blood cells are part of this system * Phagocyte – a type of white blood cell that will eliminate the virus by engulfing then digesting the bacteria, the process of this is called phagocytosis. * Lymphocyte – a type of white blood cell that carry antibodies * Antigen – certain chemicals that are foreign to the body in pathogens * E.g.: 1. James is infected by some bacteria that cause a disease. 2. The bacteria reproduce and produce toxins that make James ill 3. A white blood cell detects the bacteria and it makes antibodies to attach to it. Other white blood cells engulf the labelled bacteria and destroy them 4. The white blood cells that produce the right antibodies reproduce meaning there are lots of them making antibodies 5. Most of the white blood cells that make this antibody die, but there are few that stay in the blood called memory cells 6. The bacteria are killed and James gets better 7. He is then infected by the same bacteria 8. The memory cells that stayed in James’ blood from last time respond quickly and kill the bacteria before he becomes ill * Memory cell – a type of white blood cell that stay in the blood after the infection has been fought off * They respond quickly when it