1. A View of the Cell The Discovery of Cells p.171-174

2. The History of the Cell Theory Before microscopes were invented, people believed that diseases were caused by curses + supernatural powers Microscopes opened the world to microorganisms Microscopes enabled scientists to study cells – the basic unit of living things

3. Light Microscopes 1600s –Anton van Leeuwenhoek –Made the first microscope Compound Light Microscope –Uses a series of lenses to magnify objects –Can magnify up to 1500x

4. Compound Light Microscope

5. The Cell Theory Robert Hooke –English scientist –Studied cork – dead cells of oak bark –noticed repeated geometric box- shaped structures – called them CELLS

6. The Cell Theory Several scientists extended Hooke’s observations and came up with important conclusions –Schleiden Botanist – concluded that plants were made up of cells –Schwann Zoologist – concluded that animals were made up of cells

7. The Cell Theory The observations + conclusions of these scientists are summarized as one fundamental idea of modern biology – the Cell Theory: –All organisms are composed of one or more cells –The cell is the basic unit of structure + organization of organisms –All cells come from preexisting cells

8. Electron Microscopes 1930s + 1940s – electron microscope was developed Uses a beam of electrons to magnify objects up to 500,000x the original size Specimens must be viewed in a vacuum Disadvantage? –Cannot use living specimens

9. Two Types of EMs Scanning Electron Microscope (SEM) –Scans surface features –Creates a 3-D image Transmission Electron Microscope (TEM) –Capable of seeing internal cell structures

10. Two Basic Cell Types All cells contain small, specialized structures called organelles –Many are surrounded by membranes –Each has a specific function in the cell

11. Prokaryotes Cells that do not contain any membrane- bound organelles Many are unicellular organisms, such as bacteria

12. Eukaryotes Cells that contain membrane-bound organelles Many are multicellular but some may be unicellular, such as yeasts or amoebas

13. Prokaryote vs. Eukaryote Organelles benefit eukaryotic cell –Separates chemical reactions inside the cell so many can happen at one time Robert Brown+ Rudolf Virchow –Observed a prominent structure inside the eukaryotic cell that is responsible for cell division NucleusNucleus –Central membrane bound organelle that manages or controls cellular functions –AKA – “the brain of a cell”