Bacteria have a number of special structures outside their cell wall that help in their survival as microorganisms. Two of the structures that will be discussed here are pili and glycocalyx. Pili, also known as fimbriae, may be one to several hundreds of hairlike rods that extend from the cell walls of gram-negative bacteria. As compared to flagella, they are shorter in length and more linear. They are basically made up of subunits of pilin that are organized in a helix form. Glycocalyx, secondly, also known as slime layer, is a coating made up of polysaccharide that provides a covering to many bacteria (Levinson, 2004).
The main function of pili is to provide a bond of interaction between the bacteria and human cell surface receptors. This is an essential stage of the infective properties for certain bacteria. Moreover, a special type of pilus, the F pilus, enables contact between the donor and recipient bacteria during the process of sexual reproduction (conjugation). The functions of glycocalyx include rigid attachment of bacteria to structures like skin, heart valves, and teeth, hence, playing a significant part in oral plaque (Taylor, Green & Stout, 2003) (Levinson, 2004).
Certain structures present in a plant cell are not found in a bacterial cell. Two such structures are mitochondria and chloroplasts. Mitochondria are elongated structures consisting of a double layered envelope with the inner layer forming cristae (foldings). They are filled with chlorophyll and a matrix that contains ribosomes, a circular DNA and phosphate particles. The cristae and matrix are responsible for oxidative phophorylation and Krebs cycle enzyme formation, in cell respiration, respectively.
Chloroplasts are also double layered but large structures. They have a gel-like stroma that comprises of grana (a membrane network), ribosomes, circular DNA, and lipid droplets. They are the site of photosynthesis, conversion of light to usable chemical energy using CO2 and water (Taylor, Green & Stout, 2003)
Levinson, Warren. (2003). Medical Microbiology & Immunology. USA: McGraw-Hill Companies, Inc. Taylor, D. J. , Green, N. P. O. , & Stout, G. W. (2003). Biological science. Cambridge: Cambridge University Press.
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