Immune System and Disease essays

Immune System and Disease essays Today, our world is faced with many diseases. Some havent been discovered and some have no cures. The immune system fights off many of these diseases, but what happens when it fails us? One of the most deadly, incurable disease the world is faced with today is the Human Immunodeficency Virus (HIV). There is no none cure yet. Viruses cause colds and the flu. Viruses are microscopic particles that invade the cells of plants, animals, fungi, and bacteria. They often destroy the cells they invade. How do viruses reproduce? A virus first enters a cell in one of three ways: direct penetration, endocytosis, or membrane fusion. The virus takes over the cells machinery and is thus forced to make the viruss proteins and RNA. When the virus has entered, viral RNA is released in to the cell and reverse transcriptase occurs. Reverse trancriptase is when the cell makes a DNA copy of the viral RNA. It then produces the proteins and genes the virus needs to be assemble. The virus can then be released by three ways: lytic, lysogenic, and persistent. A virus, although not considered to be alive, does have a life cycle. First the virus attaches to a cell, which it recognizes by its surface markers. Then it penetrates the cell and gets inside. Next, it replicates and makes copies of itself. It then assembles itself back together and the new viruses are released. A virus cannot replicate by itself; it has to infect a cell. The virus is always the same size. It doesnt have a metabolism. A virus has three different shapes it can be: helical, polyhedral, and enveloped. It is made up of nucleic acid (RNA or DNA), and surrounded by a protein coat. Certain viruses can survive harsh conditions. Pathogens, disease-causing agents, have to enter the body to cause illness. There are several ways for them to get into the body: through the genitals, breaks in the skin, and natural openings. The immune system...