The Structure of Prokaryotic and Eukaryotic cells.

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Alice Unwin

Essay 2: Prokaryotic and Eukaryotic Cells.

The Structure of Prokaryotic and Eukaryotic cells

        The prokaryotic cell developed first, pro meaning before and karyon meaning nucleus. The evolution of prokaryotic cells preceded that of eukaryotic cells by 2 billion years. This group of cells are now known as bacteria and archae. This simple cell has evolved into the eukaryotic (true nucleus) cells, a more complex cell, generally found in higher organisms such as plants and animals.

The fundamental difference between the two cells is the presence of a nucleus in the eukaryotic cell. Though the prokaryotic cell contains genetic information, it is suspended freely in the cytoplasm. The eukaryotic cell is also considerably larger than the prokaryotic, it possesses an endoplasmic reticulum along with many other complex organelles and synthesises larger ribosomes. On the other hand all prokaryotic cells have cell walls, where as it is generally only the eukaryotic cells of plants that possess cell walls.

In this essay, the similarities and differences between these two cells will be discussed along with exploring which cell is more primitive and why.

The Prokaryotic Cell

The Eukaryotic Cell

Scientists believe that the eukaryotic cell originated from several different types of prokaryotic cell, hence the similarities between the two cell types. The contents of both cells are suspended in the cytoplasm, due to the merging of cells in order to form the eukaryotic cell; the structure of the cytoplasm is the same in both cells. However, the “control centre” of the cell, is the main division between the two groups.

The nucleus of the prokaryotic cell consists of a dense bundle of chromosomes, bound by a nuclear envelope. This envelope is a double membrane that controls the substances that enter and exit the cell. The chromosomes of a prokaryotic cell are freely suspended in the cytoplasm and are circular; this DNA ring is known as the nucleoid and is not compartmentalized by a double membrane or envelope although it is concentrated to certain areas of the cell. There are approximately 2000 chromosomes in the prokaryotic cell, just 0.2% of those present in the eukaryotic cell. There are also smaller rings of DNA known as plasmids, which act as additional chromosomes. The dissimilarity between this organelle shows a progression from the prokaryotic cell to the eukaryotic cell and the complexity of it compared to the prokaryotic cell.

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An Electron Micrograph Of The Eukaryotic Nucleus

Suspended within the cytoplasm, as well as the nucleus, the eukaryotic cell possesses many other membranous organelles that the prokaryotic cell lacks.

The endoplasmic reticulum in the eukaryotic cell comes in two forms, rough and smooth. It is made of flattened cavities lined with membrane sacs. The rough endoplasmic reticulum is responsible for the transport of proteins. It is rough because it is covered in ribosomes, which synthesis the proteins. The function of the smooth endoplasmic reticulum is to transport lipids and steroids around the cell. ...

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