Viruses Essay Research Paper Today our world

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Viruses Essay, Research Paper Today, our world is faced with many diseases. Some haven?t 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 cell?s machinery and is thus forced to make the virus?s 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 doesn?t 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 usually stops these invaders from getting in. The primary way to stop pathogens is by the skin. But, the skin has natural openings where they can get in. The eyes, ears, nose, mouth, and genitals are all natural openings. The second line of defense is at these natural openings. The pathogens get stuck in the mucus lining of the nose and mouth or are killed by the saliva and stomach acids; tears from the eyes;

earwax; and acidic secretion of the vagina all stop pathogens but they don?t get them all. The third line of defense is the Tortiory Response. There are two different kinds, innate (which you are born with and is non-antigen specific and acquired (which you acquire through life and is antigen specific). Innate has three different reposes to it. The first: phagocytic cells eat live viruses, bacteria and, dead cells. The second: natural killer cells are non-specific and destroy all infected cells. The third: interferon binds to the surface of surrounding healthy cells and activates their genes to create an antiviral state. Acquired immunity has different parts to it: macrophages (ingest viruses and expresses information to other cells; intructs and recognizes), T4-cells (instruct),

T8-cells (respond), B-lymphocytes (respond), and lymphokines (rate control). There are two different kinds of acquired immunity: humoral and cell mediated. The humoral response involves the production of antigen-specific antibodies. Those antibodies neutralize he virus, help macrophages ingest and T8-cells to destroy it, and cause the destruction of the viral envelope. Colonal selection is part of the humoral response. The T4-cells get the right B-cells and activate them. The B-cells produce antibodies quickly then start to divide. Once they divide, they are called plasma cells and are able to produce 2,000 antibodies per second for 4-5 days. The cell-mediated response develops T8-cells that destroy host cells that have been infected already. T8-cells can tell the difference