Compare and contrast a motor nuerone and a bacterium
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The aim of this essay is to compare and contrast a salmonella bacteria (prokaryotic) cell with a motor neurone (eukariotic) cell. Cells are the basic structures contained in all living organisms, their function, size and shape differ depending on which organism serves as its host. They are catagorised as either eukaryotic or prokaryotic cells, prokaryotic being the old Greek term meaning 'before nucleus'. It wasn't until the 17th century that cells were discovered by the European Antonie van Leeuwenhoek with his latest invention - a very primitive microscope. These new discoveries were later named by an English scientist by the name of Robert Hooke. (Wikipedia 2007) The eukaryotic cell can be found in either animals or plants, although the two are very different in both structure and function. The animal cell has a complex internal structure containing many membrane bound organelles that individually have a defined role to play within the cell - more detail will be given about the motor neurone later in this essay. Most animal cells have the same basic parts, namely, nucleus, cell membrane, and cytoplasm with various membrane bound organelles (see appendix 1). The prokaryotic (bacteria) cell has a more basic structure (see appendix 1)
The salmonella cell is surrounded by fibres similar in appearance to the dendrites known as flagella, however, the function of the flagella is to allow the cell to move through the intestines of its host, the name given to this function is motile. The bacteria cell can also increase its surface area although internally, by creating mesosomes - folds which protrude inside the cell membrane. The point at which two neurons connect, or the connection between a neuron and muscles or glands occurs is the synapse. Some cells in the nervous system can have as many as 200,000 of these connections and it is at this connection that 'electrochemical communication' occurs and the electrical and chemical signals are sent and received. The bacteria cell also has the ability to attach to other cells but not for the purpose of electrochemical communication but for 'conjugation' - a primitive form of reproduction, which it does with the use of an external appendage known as pili. The cell body or soma of the neurone is a hive of metabolic activity and contains the nucleus, a double membrane bound organelle, (usually rounded in the animal cell) with nuclear pores.
They both contain a type of genetic blueprint known as DNA and RNA, needed for both species to function and reproduce. They possess the specialised machinery to manufacture this, that said, there are even differences here. The motor neurones DNA is linear or has closed ends and contains proteins named 'histones', which are organised into chromosomes. The salmonella bacteria has naked DNA that forms a chain and does not contain these histones, therefore, has no end and no beginning, it is just a loop of DNA. (class notes 2007, Boyle & Senior 2002) Both cells In conclusion, whilst these two organisms are the building blocks of life, they share minimal features. Both have a cell membrane, contain DNA and contain ribosomes within cytoplasm. Here the similarities end, the motor neurone cell is far more complex in structure and function than the basic salmonella cell. Its contents include many membrane bound organelles including the nucleus, synapse, dendrites and the axon with its own specialised features. The salmonella has flagella to facilitate movement, naked DNA and the protection of a capsule. They each have aspects of their own make-up that are unique, but basically they are one and the same, however, one has, over many millions of years evolved from the other. The bacterium and its simplistic form has clearly been a key to its longevity.
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