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  • Date Submitted: 07/24/2011 10:01 PM
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5. The Fundamental Unit of Life
 Cell: It is the smallest unit of life capable of performing all living functions.  Milestones in Cell Biology Biologists Major contributions Discovered cell  Robert Hooke Discovered microscope  Leeuwenhoek Nucleus  Robert Brown Coined term protoplasm  Purkinje  Schleiden and Schwann Presented Cell theory First described Golgi apparatus  Camillo Golgi  Cell theory  All plants and animals are composed of cells  The cell is the basic unit of life.  This was further expanded by Virchow by suggesting that all cells arise from pre-existing cells.  Unicellular organism – It is made up of only a single cell, e.g. Amoeba, Paramecium  Multicellular organism – It is made up of many cells, e.g. algae, plants, animals, etc. Structural organization of cell  Cell wall – It is the outermost structure present in plant, fungal, and some bacterial cells; it is absent in animal cells  Plasma membrane or cell membrane – It is the outermost covering of all cells. It separates the contents of the cell from the external environment. Important functions of cell membrane:  Regulates the entry and exit of substances in and out of the cell  Performs certain physical activities such as diffusion and osmosis o Diffusion – It is the spontaneous movement of molecules from a region of high concentration to a region of low concentration o Osmosis – It is the movement of water molecules from a region of high concentration to a region of low concentration, through a selectively permeable membrane  Cytoplasm – It is the fluid that fills the cell; It contains all cell organelles

Cell organelles  Nucleus  It controls all the cellular activities of the cell; acts like the brain of a cell.  Important components of nucleus are nuclear membrane, nucleoplasm, containing chromatin and nucleolus  Prokaryotic cell - The nuclear region is poorly defined; membrane-bound organelles are absent. The undefined nuclear region containing only nucleic acid is...

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