Viruses, Bacteria, and Prions

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Viruses, bacteria, and prions are all quite different, but they all share one commonality: they can all cause disease in humans. All three are also organic, in one way or another. Despite this, only bacteria are properly alive by most definitions. Bacteria are also the most complex, followed by viruses, and then finally, prions.


As mentioned in the introduction, bacteria are the most complex organizations that will be covered in this paper. Bacteria were among the first forms of life to evolve on Earth about 3.5 million years ago. This has allowed them to become one of the most diverse groups of life, from the photosynthetic cyanobacteria, to the parasitic bacteria that infect humans.

Despite being so diverse, bacteria are rather simple in structure compared to eukaryotes such as ourselves. They are prokaryotic, unicellular organisms, meaning that they have neither membrane-bound nuclei nor organelles and exist independently of each other, although they often form colonies. Although bacteria lack organelles in the eukaryotic sense, they do possess ribosomes to manufacture proteins, and a special area called the “nucleoid” that contains the circular chromosome. Surrounding all of this is the cytoplasm, in which a majority of the chemical reactions of a bacterium take place. The cytoplasm itself is then bound by an inner membrane, a rigid cell wall, and in certain species, an outer capsule.

Bacteria, unlike more complex organisms, have multiple different pathways for reproduction. The most commonly used of these paths is binary fission in which the chromosome is duplicated and then the cell simply splits in two. This pathway, however, does not allow for the exchange of genetic information, so bacterial cells ofte...

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