THE STRUCTURE OF CELLS
Prior to 1655 when Robert Hooke observed the cells of a cork tree through an antiquated microscope, the whole idea of cells were perhaps unknown or at best speculative, if it even dawn on the thoughts of average men, as to where all life form and organisms came from. (http://www.biology.arizona.edu) Subsequent to this discovery, not much occurred, except the discoveries of protozoa and bacteria by Leewenhoek. Not until almost two centuries thereafter could mankind celebrate the biological discoveries by Schleiden and Schwann. Their conclusion from research became what is called the Cell Theory. (http://www.biology.arizona.edu)
According to the Cell Theory, (the modern theory) all living organisms emanate from cells. The cell forms the structural and functional unit of living organisms and all cells come from pre-existing cells by means of division. (http://www.bio.miami.edu/~cmallery/150/unity/cell.text.htm) They are the smallest form of life and are also known to be responsible for all energy flow of life that occurs within living organisms. In terms of chemical composition, cells are basically the same. (http://www.bio.miami.edu)
Single celled organisms such as bacteria and protists are referred to as unicellular. While life forms such animals, plants or fungi are classified as multicellular.
Although living organisms consist of multiplicity of cells there are only two major classes of cells. They are namely, Prokaryotic and Eukaryotic. Whether cells can be classified as the former or the latter, they have a set of common features. (http://www.phschool.com) Deoxyribonucleic acid, or DNA for short, is the genetic substance contained in one or several chromosomes. It is located within the nonmembrane bound nucleoid region in prokaryotic cells and situated in a membrane-bound nucleus in Eukaryotic cells. (http://www.phschool.com) Another feature that is shared between the major cell groups entails the plasma membrane. This...