Why We Study the Cell and Its Components
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Why We Study the Cell and its Components
A cell is the basic of the living unit. The cell theory states that all living things are composed of cells and that all cells come from other cells.(Campbell 2010. P.57) Living organisms may be composed of one or many cells that carry out living activities. Both animals and plants are comprised of cells. Also there is the world of bacteria that we cannot see with the naked eye. The two basic cellular constructions are the prokaryotes and eukaryotes.
Prokaryotic cells do not have a nucleus and are the oldest of the two cell constructions; they date back as far as three and a half billion years ago. Almost all species of prokaryotes have cell walls exterior to their plasma membranes. The two major branches of prokaryotic evolution are bacteria and archaea. Some bacteria are harmful and even deadly to humans; it can cause infections and diseases. However the largest percentage of bacteria is essential to life. Among the archaea are the methanogens that can live in oxygen free environments. They inhabit the digestive tract in animals and aid in the digestion of animals that depend on plants for their nutrition. (Campbell 2010. P.303)
Eukaryotic cells do have a nucleus and also several membrane bound organelles that are not present in prokaryotic cells. Eukaryotic cells first appeared around a little more than town billion years ago. The organelles found in eukaryotic cells are mini organs specialized for the tasks needed for the cells to function and survive. The most obvious organelle in any eukaryotic cell is the nucleus. The nucleus contains the DNA the activity of the cell. The nucleus is surrounded by a membrane called the nuclear envelope that controls the flow of molecules between the nucleus and the rest of the cell.