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Discuss how Prokaryotes are the same as Eukaryotes.

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Introduction

Discuss how Prokaryotes are the same as Eukaryotes All living organisms can be classified into two distinct groups: eukaryotes and prokaryotes. These two groups are classified on the basis of their cell structure. The barrier between the two groups essentially divides single-celled primitive cells from the more complex variety of multicellular organisms. In truth, however, the word, eukaryote can be broken into eu from the Greek meaning "truly", and karyon meaning "nucleus", in combination, reading "truly nucleated". Although both eukaryotes and prokaryotes contain common structures, each has its own distinguishing features. Prokaryotic cells have no membrane-bound organelles. This means their DNA is naked, circular and lies free in the cytoplasm, and forms a plasmid. Eukaryotic cells, on the other hand, have double membrane-bound nuclei in which the non-circular chromosomal DNA is contained. Eukaryotes have much larger mass due to their greater size. A bacterium such as E. coli has a mass of about 0.5p; a eukaryotic cell 30�m in diameter has a mass of 14ng. Eukaryotes therefore have a surface area to volume ratio of more than 10 times lower than that of prokaryotes. Eukaryotes are also 10-50 times the length or diameter of prokaryotes and therefore house larger varieties of ribosomes i.e. they contain 22nm ribosomes rather than the 18nm ribosomes in prokaryotes. ...read more.

Middle

All eukaryotic organisms are formed from many cells clustered together, each with their own specific role, and often gathered into groups of similar cells, called organs. In this way, it can be seen, that both types of cell, can act as building blocks for larger organisms. These common features may be thought to be related to the idea of a common ancestor. This theory suggests that all living organism originated from a common cell, which then divided into different groups via speciation methods. Common features are also related to the endosymbiotic theory, which proposes that eukaryotes evolved from prokaryotes. Eukaryotes contain ribosomes that are semi-autonomous, and have their own DNA, ribosomes, mRNA and tRNA. It was gradually realised that DNA, RNA and protein synthesis in mitochondria and chloroplast display more similarities to the cognate processes in prokaryotic cells than to those in eukaryotic cells. From this realisation, came the endosymbiotic theory which adds to the argument that prokaryotes are the same as eukaryotes, because from this theory, one can see that eukaryotes are heavily dependent on the processes that prokaryotes have given them in this symbiosis. It is the transformation of chloroplasts and mitochondria from prokaryotes that has allowed eukaryotes to respire especially in atmospheres lacking in oxygen; and since these features are two of ...read more.

Conclusion

A feature of eukaryotes is also their ability to transport materials into and out of the cell in bulk, i.e. not just by diffusion by carrier proteins in the cell membrane. They can do this via endocytosis and exoxytosis, processes which are unique to eukaryotes. In endocytosis, portions of the membrane invaginate and are pinched off to form membrane-bounded cytoplasmic vesicles, containing substances that were previously on the outside of the cell. Exocytosis is the opposite of this process and involves membrane-bounded vesicles inside the cell fusing with the plasma membrane and releasing their contents to the outside of the cell. As a summary, it has been shown that eukaryotes and prokaryotes have many cellular similarities, as do many different organisms, but in general, they differ greatly in their morphological structure, and hence the reason they are classed into different taxonomist classifications. Word Count = 2057 Becker, W.M., Kleinsmith, L.J. and Hardin, J. (2000). The World of the Cell. 4th ed. San Francisco: The Benjamin/Cummings Imprint. Jones, M., Fosbery, R. and Taylor, D. (2000). Biology 1. Cambridge, Cambridge University Press. Jones, M. and Gregory, J. (2001). Biology 2. Cambridge: Cambridge University Press. Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K. and Walter, P. (2002). Molecular Biology of the Cell. 4th ed. New York: Garland Science. Biology of Cells supervision (Sarah Jarmin) Jessica Beveridge Due 28/10/02 ...read more.

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