Mononucleus Essay Research Paper MononucleusBacteriaThe smallest living

Mononucleus Essay, Research Paper

MononucleusBacteriaThe smallest living things on earth are the prokaryotic cells. Bacteria fall into the Monera Kingdom. They have a single DNA molecule in the cytoplasm. Almost all monerans have a cell wall that protects the cell and gives it its shape. Some monerans have a layer outside the cell wall called the capsule. This helps the cell cling to surfaces.A typical bacterium is about 2 micrometers long. Inside the cell, there are nucleic acids, enzymes, and other substances necessary to carry out the cells life process. Bacterium have long , thin, hairlike structures called flagella. They act as a propeller, as they rotate and move in response to chemical stimulation. Some have strands of pili , which enables them to stick itself to a surface.Some shell shapes important in classifying monera are: spherical cells, called cocci ; Rod shaped cells called bacilli, and spiral shaped cells called spirilli. There are over 16,000 species of monerans. Bacteria Showing Flagella Disease Causing BacteriaTwo main groups of bacteria exist: the saprophytes, which live on dead animal and vegetable matter; and the symbionts, which live on or in living animal or vegetable matter. Saprophytes are important because they decompose dead animals and plants into their constituting elements, making them available as food for plants. Symbiotic bacteria are a normal part of many human tissues, including the alimentary canal and the skin, where they may be essential to certain processes. Bacteria are involved in the spoilage of meat, wine, vegetables, and milk and other dairy products. Bacterial action may render such foods unpalatable by changing their composition. Bacterial growth in foods can also lead to food poisoning such as that caused by botulism. On the other hand, bacteria are of great importance in many industries. The fermentative capabilities of various species are used for the production of cheese, yogurt, pickles, and sauerkraut. Bacteria are also important in the production of tanned leather, tobacco, textiles and various enzymes, polysaccharides, and detergents.About 200 species of bacteria are pathogenic, or disease causing, for humans. Pathogenicity varies widely among various species and is dependent on both the harshness of the particular species and the condition of the host organism. The bacteria responsible for human disease are those that cause cholera, lockjaw, gas gangrene, leprosy, plague, bacillary dysentery, tuberculosis, syphilis, typhoid fever, diphtheria, undulant fever, and several forms of pneumonia. Until the discovery of viruses, bacteria were considered the causative agents of all infectious diseases. VirusesViruses are submicroscopic parasites that consist of either RNA or DNA, but never both. There is also a protective coat of protein or of protein combined with lipid or carbohydrate components. The nucleic acid is usually a single molecule, either singly or doubly stranded. Some viruses, however, may have nucleic acid that is segmented into two or more pieces. The protein shell is termed the capsid, and the protein subunits of the capsid are called capsomeres. Together these form the nucleocapsid. The complete virus particle is called the virion. Viruses replication can take place only in actively metabolizing cells. Outside of living cells, viruses exist as idle macromolecules. The smallest viruses are icosahedrons (20-sided polygons) that measure about 18 to 20 nanometers wide (one-millionth of a millimeter = 1 nanometer). The largest viruses are rod shaped. Some rod-shaped viruses may measure several microns in length, but they are still usually less than 100 nanometers in width. Therefore, the widths of even the largest viruses are below the limits of the light microscope, which is used to study bacteria and other large microorganisms. “Virus Structure”To cause new cases of disease, viruses must be spread from person to person. Many viruses, such as those causing influenza and measles, are transmitted by the respiratory route when virus-containing droplets are put into the air by people coughing and sneezing. Still others, such as yellow fever and viruses called arboviruses, are spread by biting insects. Viral diseases are either endemic (present most of the time), causing disease in susceptible persons, or epidemic that is, they come in large waves and attack thousands of people. The only effective way to prevent viral infection is by the use of vaccines. For example, vaccination for smallpox on a worldwide scale in the 1970s eradicated this disease. Many antiviral vaccines have been developed for humans and other animals. Those for humans include vaccines for rubeola (also known as measles), rubella, poliomyelitis, and influenza. Immunization with a virus vaccine stimulates the body’s immune mechanism to produce a protein called an antibody that will protect against infection with the immunizing virus. The viruses are always altered before they are used for immunization so that they cannot themselves produce disease.

Upper Left – Aids VirusUpper Right – Chicken PoxLower Left – RabiesLower Right – Hepatitis BMononucleosisMononucleosis is a common viral illness common among young adults. It is transmitted by mucus or saliva, either through direct contact (for that reason the nickname the “Kissing Disease”), or by airborne droplets of saliva or mucus. The usual symptoms of mononucleosis are fever, sore throat, swollen lym