Compare And Contrast Bacteria And Bacteria

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Question 1A: Compare and contrast the general structure of a virus and a bacterium.
Bacteria and viruses both do not contain a DNA enclosing nucleus; however, these organisms differ greatly in the complexity of their structures. Generally a bacterium is encompassed within a semi-rigid cell wall made of peptidoglycan, which provides structural support. It is classified as gram positive if its cell wall is thick and stains purple when tested for identification. If its cell wall is thin and stains red, it is referred to as gram negative. Under the cell wall, the bacterium also has a plasma membrane made up of a phospholipid bilayer with proteins inserted inside. Within its cytoplasm, ribosomes for protein synthesis and a single DNA strand are
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Some bacterium also has additional nucleic acid inside a plasmid in the cytoplasm. A sticky slime layer or capsule consisting of polysaccharides called glycocalyx can be found at the cell surface of some bacterium. Further, rigid filaments called flagella and outer cell surface appendages called pili and fimbriae, which are hair-like structures, can be found on others. The classification of a bacterium is dependent on its size, shape (spherical, rod or spiral), colour and by how it is arranged together (staph (bunched), diplo (2) or strep (line)). In contrast a virus typically only consists of a core of nucleic acid (either single or double stranded DNA or RNA) for viral replication and a protein coat (or capsid) of symmetrically arranged repeating protein units called capsomeres. Some virus in addition may contain an inner protein layer surrounding the genetic material and others an outermost spiky layer termed the envelope that consists a lipid bilayer with embedded viral proteins. Unsurprisingly, …show more content…
Mitosis takes place in most body cells (somatic cells) and has an important role in tissue repair, growth and development hence genetic make-up must be the same for each cell. In contrast, meiosis only occurs in gonads (sex cells) and forms gametes for sexual reproduction, which requires genetic variability and only half the genetic material. The basic series of occurrences in mitosis are similar to that of those in meiosis. They both consist of the disintegration of the nucleus membrane, the splitting of genetic material, subsequent cell division and reestablishment of the nuclear membrane into two cells. This represents one division, which comprises of the processes of prophase, metaphase anaphase, and telephase. The fundamental contrast is that meiosis involves two successive divisions of a diploid (2N- 2 sets of chromosomes) cell where DNA replication is absent between the two cellular divisions while mitosis only involves one. Moreover, in meiosis I (first division) homologous chromosomes join together, cross over, and align randomly at the metaphase plate in tetrads (exchanging chromosomes) creating significant variations in resulting gamete cells. In accordance, mitotic cell division produces two genetically identical diploid daughter cells, each with the total sum of chromosomes (46) as the mother cell (diploid 2N). In contrast, meiosis

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