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Cell Theory

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Biology HL Portfolio

The Cell and Cell Theory

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The cell

The word cell comes from the Latin word “cellula”, which means a small room. The cell is the smallest unit of a living organism, also known as “the building block of life”. Every living organism is consisted of a cell. There are bacteria (unicellular organisms), and multicellular organisms. There are different types of cells, prokaryotic and eukaryotic cells. All cells come from preexisting cells. “Every cell is self-maintaining; it takes in nutrients, converts them into energy, carries out special functions and reproduces itself if necessary.” The descriptive name for the smallest living biological structure was given by Robert Hooke in a book, which he published in 1665, while discovering “small units” in a cork. After that the research of the cell has progressed greatly.

Cell structure
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http://sun.menloschool.org/~cweaver/cells/e/nucleus/cellpic.jpg

Prokaryotic and Eukaryotic cells

There are two types of cells. While they are still cells which make them have a lot of similarities, they are also very different. The main difference between them is that a prokaryotic cell does not consist of a nucleus nor a nuclear membrane, while the eukaryotic on the other hand does. There are two types of prokaryotic cells, bacteria and archaea. The plasma membrane of the cell protects it from the outside environment. Most of them also have cell walls, but there are exceptions to that. Since the cells don’t have a nucleus the DNA is stored in the nucleoid. [pic]

http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg

The eukaryotic cell looks like this. They are around 10 times bigger than the prokaryotic cell. Unlike the prokaryotes they have a cell nucleus, where the cell’s DNA is stored, and a cell membrane. All of it’s chromosomal DNA is stored in the cell nucleus. The mitochondria in the eukaryotic cell also contain some of the DNA.

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