Cells101 - Cell 1 Just as the atom is the fundamental unit...

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Cell - 1 Just as the atom is the fundamental unit of matter, the cell is the fundamental unit of living organisms. Each cell is unique, composed of carbohydrates, proteins, lipids, and other substances, 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. History of the cell The study of cells dates back more than three hundred years, coinciding with the development of microscopes. As scientists over the years learned more about cells, a group of common characteristics was developed which we call the Cell Theory. Our use today of more sophisticated microscopes and research on biochemical cell activities reinforces these premises. The Cell Theory 1. Every living organism is made up of one or more cells. 2. Cells are the structural and functional unit of living organisms. The smallest living organisms are single cells, and cells comprise the functional units of multicellular organisms. 3. All cells arise from preexisting cells ensuring the continuity of life. Basic Cell Features (Common to All Cells) Plasma (cell) membrane The plasma membrane is the boundary between the cell and its environment. The plasma membrane isolates the cell, regulates what enters and leaves the cell, and allows for interaction with other cells. The plasma membrane is comprised of phospholipid layers with proteins embedded throughout. The diversity of proteins found within membranes are responsible for most membrane activity. We will discuss membrane structure and function a bit later. Genetic material: nucleus or nucleoid Each cell contains genetic material (DNA), which stores the instructions for that cell's structure and function. DNA may be found within a membrane - bounded nucleus, (eukaryotic organisms – plants, animas, protists and fungi) or simply concentrated in a region of the cytoplasm called the nucleoid (prokaryotic organisms - Eubacteria and Archaebacteria). Cytoplasm Cytoplasm includes the fluid matrix (called the cytosol) inside the plasma membrane in which everything else in the cell, such as internal membranes, particles and membrane-bounded structures, called organelles, are suspended.
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Cell - 2 Cell Organization and Cell Dimensions While the benefits of a cellular organization seem fairly clear, we must look more closely at how a cell functions to understand why most cells are very small, and why multicellular organisms are comprised of many, many microscopic cells, rather than just a few enormous ones. Each cell needs to perform a number of functions while maintaining a pretty constant internal environment. Cells must exchange materials with the external environment, and undergo any number of chemical reactions, each with specific chemical requirements, in order to stay alive and do their jobs.
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Cells101 - Cell 1 Just as the atom is the fundamental unit...

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