Discovery of the Cell Robert Hooke 1665 English
Discovery of the Cell • Robert Hooke (1665) – English scientist – looked at a thin slice of cork (oak cork) through a compound microscope – observed tiny, hollow, room-like structures – called these structures “cells” because they reminded him of the rooms that monks lived in – only saw the outer walls (cell walls) because the cork cells were not alive
Discovery of the Cell • Anton van Leeuwenhoek (mid 1600 s) – Dutch fabric merchant and amateur scientist – looked at blood, rainwater, scrapings from teeth through a simple microscope (1 lens) – observed living cells; called some “animalcules” – some of the small “animalcules” are now called bacteria
Major Events in Cell Biology and Imaging
Development of Microscopes • van Leeuwenhoek’s microscope was considered a simple light microscope because it used one lens and natural light • Hooke’s microscope was compound because it used two lenses
Development of Microscopes • In the 200 years after Hooke, compound light microscopes have improved to magnify objects 1500 times using two lenses and a beam of light • Electron microscopes use a beam of electrons to magnify objects 500, 000 times! – This power allows us to see the structures on the surface and within the cell
Electron Microscopes • Scanning Electron Microscope (SEM) – Scans the surface of cells to show their threedimensional shape • Transmission Electron Microscopes (TEM) – Sends electrons through a specimen to show the parts inside the cell • Scanning Tunneling Microscope – Uses electrons to investigate atoms on the surface of a molecule
• Scanning Electron Microscope (SEM) • Transmission Electron Microscopes (TEM) • Scanning Tunneling Microscope
Compound Light Microscope Eyepiece Body Tube Revolving Nosepiece Arm Objective Lenses Stage Clips Diaphragm Stage Coarse Adjustment Fine Adjustment Light Source Base Source: http: //www. biologycorner. com/microquiz/
Eyepiece – lens magnifies 10 x Arm – Always carry with one hand on the arm and one on the base Stage – Supports the specimen slide Coarse Adjustment – moves stage up or down to bring specimen into focus Fine Adjustment – allows for precise focusing Base – supports the scope
Body Tube – supports the eyepiece and objectives Revolving Nosepiece – holds and rotates objective lenses ** Objective Lenses – magnify by 4 x, 10 x, 40 x, or 100 x Stage Clips – hold the specimen slide to the stage Diaphragm – controls the amount of light reaching the stage Light Source – provides the light that shines through the stage ** Since the eyepiece had a magnification of 10 x, the total magnification when using the 4 x objective lens would be 40 x. When using the 10 x objective lens, the total would be 100 x. When using the 40 x lens, the total would be 400 x.
Cell Theory • Two scientists, Matthias Schleiden and Theodore Schwann (1830 s) expanded upon Hooke’s observation of “cells” • Their observations in plants and animal cells have been summarized as the Cell Theory • The Wacky History of Cell Theory
The Cell Theory • 1. All organisms are composed of one or more cells • 2. The cell is the basic unit of organization of organisms – Unicellular organisms – made of one cell that must perform all life’s activities – Multicellular organisms – made of more than one cell. Each cell performs most of the major functions of life • 3. All cells come from preexisting cells – Before the cell theory, people did not know where these cells came from. People learned that a cell divides to form two identical cells – The ability of a cell to divide is the basis for • all reproduction (sexual and asexual) • Growth and repair of all multicellular organisms
- Slides: 12