Starch, Cellulose, Dextran, and Glycerate - Essay Example

Microbiology 16-Jan In 1835, Bassi showed that a fungus caused a silkworm disease, and in 1865 Pasteur discovered that a protozoan caused another silkworm disease. Why do we use Kochs postulates instead of Bassis or Pasteurs postulates? Koch was among the first scientists who discovered that bacteria cause disease after he proved disease-causing pathogens and correlated them to the specific diseases. He used four guidelines to help in identification of the pathogens. These guidelines were developed using his experience with purified cultures of anthrax, which had been extracted from dead animals. Kochs postulate also proves that the disease causing pathogens could be transmitted from one organism to another. Bassi and Pasteur, however, in their research were not able to isolate the casual organism thus they were not able to identify the actual cause of the disease (Walker, 2008). Besides being able to isolate the casual pathogen, Koch also correlated the specific pathogen that caused the disease. The Kochs postulate is, therefore, commonly used because of the accuracy of the results. Additionally, Kochs postulate allows single microbes to reproduce to form more visible colony of cells thus enhancing more clarity and accuracy as compared to Bassis or Pasteurs postulates (Walker, 2008). 2. Use Figure1 above to answer the following question: starch, cellulose, dextran, and glycogenare polysaccharides. How are they similar? To what are their different properties due? Why cant an enzyme that hydrolyzes starch degrade cellulose? Similarities between Starch, cellulose, dextran, and glycogenare; Starch, cellulose, dextran, and glycogenare are similar because they are all polysaccharides with the same basic formula which is (C6H10O5) n. They are also macromolecules that can also act as storage or structural molecules (Walker, 2008). Differences One of the common property differences between these polysaccharides is that Starch and glycogenare are storage polysaccharides while Cellulose and dextran are structural polysaccharides where; Starch and glycogenare are storage polysaccharides however; starch is a plant storage polysaccharide composed of glucose while Glycogenare is an animal starch that is stord in the liver and muscles of vertebrates (Walker, 2008). Cellulose and dextran are structural polysaccharides; cellulose is the most abundant organic compound and it is made of glucose consisting of linkages 1-4. Why cant an enzyme that hydrolyzes starch degrade cellulose? An enzyme that hydrolyzes starch cannot degrade cellulose because a chain of dextran consists of 1-6 linkages between glucose molecules while in starch cellulose has beta 1->4 (Walker, 2008). Additionally enzymes are always very specific thus enzymes that hydrolyze starch cannot degrade cellulose. 3. In 1884, Hans Christian Gram described a method of staining bacterial cells while not staining surrounding animal tissues; however, he thought the staining method he developed was faulty because not all bacteria stained. In a letter to the editor of The journal in which Gram published his findings, write your response to Grams concern. Not staining the surrounding animal may not be as effective since bacteria do not all make up the cell walls the same way thus not all the bacteria absorb the stain (Walker, 2008). Therefore not all bacteria may be visible thus affecting the accuracy. The gram positive bacteria have a mono-layered cell wall that contains a lot of polymer peptidoglycan which makes the cell wall rigid (Walker, 2008). The colorizing agent used during gram staining may therefore not be absorbed as it stays on the peptidoglycan in the wall’s outer surface. Additionally, the gram negative bacteria could be having more than 40 layers of this polymer on the cell wall and peptidoglycan only makes up a small percentage of it. The cell wall may therefore fail to hold much stain on it. As a result, if the cell walls do not absorb the stain, the results from the test could be erroneous causing wrong diagnosis (Walker, 2008). 4. Compare and contrast gram-positive and gram-negative cell walls with regard to (a) sensitivity to antimicrobial agents, (b)resistance to phagocytosis, (c)chemical composition, and (d) decolorization by alcohol. (a) Sensitivity to antimicrobial agents Gram positive and gram negative cell bacteria cell walls can be identified from the gram staining technique which also determines the structural differences between their cell walls. The gram negative bacteria cell wall is more resistant to antimicrobial agents since it does not retain the stain from the colorizing agent (Walker, 2008). The gram positive bacteria cell wall on the other hand retains the stain color. The gram negative cell wall is more resistant to antibodies because of their impenetrable cell wall (Walker, 2008). (b) Resistance to phagocytosis The gram-negative cells are more resistant to phagocytosis and penicillin attacks as compared to the gram positive cells (Walker, 2008). This is because the gram-negative outer membrane contains LPS, blocks antibiotics, endotoxin, dyes and detergents which protect the cell wall and the sensitive inner membrane. (c) Chemical composition The gram positive cell wall is made up of a thin layer of peptidoglycan between the outer membrane and the cytoplasmic membrane. The gram positive cell wall on the other hand contains a thick layer of peptidoglycan than surrounds the cell. Gram-positive bacteria cell walls are made up of more than twenty times as much peptidoglycan than gram-negative bacteria (Walker, 2008). (d) Decolorization by alcohol. When decolorized using alcohol during gram staining, the gram positive cell well retains the color while the gram negative does not retain the stain color after decolorizing using alcohol (Walker, 2008). 5. Identify the catabolic pathways used by the following bacteria: Pseudomonas Oxidizes glucose It uses the Entner–Doudoroff pathway which also acts as a substitute for glycolysis. This pathway is only found in prokaryotes. This pathway is also mostly found in gram negative bacteria such as Agrobacterium, Escherichia coli, Zymomonas mobilis, Xanthomonas campestris (Walker, 2008). This pathway begins with the formation of glucose 6-phosphate and 6-phosphogluconate. Lactobacillus Ferments glucose It uses the phosphoketolase pathway. This is a where one molecule of glucose is converted to two molecules of lactic acid which is referred to as homolactic fermentation. It also causes heterolactic fermentation where carbon dioxide, ethanol and lactic acid are produced. Alcaligene Neither oxidizes nor ferments glucose It uses the Oxidative phosphorylation pathway where cells use their structure and enzymes to reform ATP. During this process, electrons are transferd from the donors to the receivers (Walker, 2008). Escherichia Oxidizes and ferments glucose It uses glycolysis pathway where glucose is converted into pyruvate. The energy produced during this process is used to form ATP (adenosine triphosphate) and NADH (nicotinamide adenine dinucleotide) which are high energy compounds (Walker, 2008). Glycolysis occurs in the cytosol of almost all organisms in both aerobic and anaerobic reactions. 6. You look in the refrigerator and find an orange drink you had forgotten was there. The drink now has an off-taste and it bubbles. What is the most likely explanation for the changes in the drink? The overstayed orange drink underwent fermentation due to the absence of oxygen in the refrigerated environment. If there is no oxygen in the environment, pyruvate is metabolized through the process known as fermentation. Fermentation involves glycolysis that also makes it possible for ATP (adenosine triphosphate) to be continually produced in the absence of oxygen. The NADH produced during glycolysis is oxidized causing the actual fermentation. The fermentation process then regenerates NAD+ which again takes part in the process of glycolysis to produce more ATP (Walker, 2008). The more the orange drink overstays in under refrigeration the more the process becomes iterative. All cells can synthesize ATP through the glycosis process. This type of fermentation can be defined as homolactic fermentation where the cells are able to perform aerobic respiration in an environment with no oxygen under extreme exertion (Walker, 2008). However there are other cells such as yeast that carry out anaerobic respiration causing alcoholic fermentation. 7. Assume that you are responsible for decontaminating materials in a large hospital. How would you sterilize each of the following? Briefly justify your answers. a. A mattress used by a patient with bubonic plague I would sterilize the mattress by first removing dust from the mattress through airing it and going over it using a vacuum cleaner. I would then use a hand held steam cleaner on the surface to get rid of germs and dust mites. To get rid of the bacteria I will spray an antibacterial spray on the surface and then spread the mattress for it to dry (Walker, 2008). This is because Bubonic plague is caused by bacteria known as Yersinia Pestis. Sterilization should therefore be done to get rid of carriers of the bacteria. b. Intravenous glucose-saline solutions I would sterilize Intravenous glucose-saline solutions using clean water, salt and minerals. I would them mix up the solution in an autoclave. The water should also be boiled to get rid of any disease causing bacteria. c. Used disposable syringe I would sterilize used disposable syringes through the heating the syringe needle until it is red hot using a burner of a candle (Walker, 2008). This will be to get rid of disease causing bacteria. Alternatively I would soak the syringe needle in alcohol or hydrogen peroxide. d. Tissues taken from patient I would sterilize the tissues through Tutoplast technique which is a chemical sterilization process used to sterilize and preserve tissues for implantation. This method is mostly used on membrane and soft tissue augmentation grafts. This method is preferable because osmotic, oxidative and alkaline treatments inactivate pathogens and get rid of bacteria (Walker, 2008). Reference Walker, T. S. (2008). Microbiology. Philadelphia, US: W.B. Saunders Company. Read More