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cell(bio) - Cell 1 A fundamental statement of life is that...

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Cell - 1 A fundamental statement of life is that all organisms are composed of one or more cells. The cell is the structural and functional unit of life. A cell is the simplest collection of matter that has the properties of life. All living organisms are composed of one or more cells. For single-celled organisms, all requirements for life: growth, development, regulation, reproduction, etc., are met within a single cell. Multicellular plants, fungi and animals are comprised of collections of cells and tissues, each with specialized structures and functions that contribute to the whole. These two statements (Living organisms are composed of cells and cells are the structural and functional unit of life) along with a third: All cells come from pre-existing cells form the cell theory . Each cell is unique, composed of molecules organized into an orderly structural and functional unit. Just as we saw that macromolecules are remarkable in their structure to function relationship, we shall, in this chapter, see how the structure of cells and, in particular, the structure of cell components, facilitates the functioning of cells. Much of what we will be discussing about cells was learned using methods we cannot see with our un-assisted eyes. Cells, for the most part, are microscopic. Moreover, when we turn to the functioning of cells, and their component parts, the organelles, we must often affect the very cell that we are hoping to learn about with our manipulations. Until the first light microscopes of 300 years ago, no one had really seen cells. However, even the best light microscope can not clearly resolve images magnified more than 1000x times (for detail about 0.2 υ m.) There are a variety of methods used to enhance the quality of images viewed with a light microscope, which, in combination, can help researchers. Until the use of transmission electron microscopes and scanning electron microscopes during the past fifty or so years, many cell components that we discuss today were not known or seen. (Electron microscopes can resolve images of about 2 nm. The scanning-tunneling microscope can generate computer surface images of single atoms magnified about 2 million times.) BCC is fortunate to have had a scanning electron microscope donated for student (and faculty) use by a local resident. As mentioned, cell biologists frequently study cell components outside of the cell using techniques such as cell fractionation, in which differential centrifugation is used to separate and isolate different organelles based on their density. Some of you will have done a cell fractionation lab in Biology 101 or in other courses. At any rate, in this chapter we are going to look at structure and organization of typical cells, based on the knowledge we have of cells today.
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Cell - 2 First, every organism is composed of one of two fundamental types of cells: prokaryotic or eukaryotic .
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