A Little History. . . English scientist, Robert Hooke (1665) • looked at cork through a compound microscope • saw tiny, room-like structures • called these structures 'cells' • saw only outer walls - cork cells are not alive • (But they used to be!)
Dutch fabric merchant and amateur scientist, Anton van Leeuwenhoek (1680) • looked at blood, rainwater, scrapings from teeth through a simple microscope • observed living cells • called these 'animalcules'
German scientists • Matthias Schleiden (1838) • Said that plants are made of cells Schleiden • Theodor Schwann (1839) • Said that animals are • made of cells Schwann • Rudolph Virchow (1854) • Said that new cells form • when old cells divide. Virchow
Cell Theory The work of Schleiden, Schwann and Virchow led to the development of the cell theory. • All living things are made of one or more cells. • Cells are the basic unit (building block) of all living things. • All cells come from cells that already exist.
Unicellular or multicellular? Some complete organisms are made of only one cell. Some are made of only a few cells.
Parts of a Cell: All cells have some very basic parts. Cell Membrane - forms the outer boundary of the cell and allows only certain materials to move into or out of the cell
Nucleus - directs the activity of a cell; it contains chromosomes made of DNA Nuclear Membrane - separates the nucleus from the rest of the cell
Endoplasmic Reticulum - moves materials around in the cell (called ER for short) Golgi Bodies - are used for packaging and secreting; “hunks” of ER pinch off to form Golgi bodies
Vacuoles - are storage areas for the cell exocytosis and endocytosis
Lysosomes • The cell’s recyclers. • The garbage men of the cell.
Cytoplasm - a gel-like material inside the cell that is made of water & nutrients
We will look at these cells! Onion cells Cheek cells (stained) Elodea cells (plant)
Microscopes micro = small + scope = to look Light Microscopes • 1. Simple • a. one lens • b. first invented in 1500’s • Compound • two lenses • We use this one in class.
Electron Microscopes • TEM • Transmission electron microscopes • invented in 1931 • two dimensional image 2. SEM • Scanning electron microscopes • invented in 1981 • three dimensional image • May be referred to as “tunneling”