Discovery of the Cell Robert Hooke (1665) –English scientist –looked at a thin slice of cork...
-
Upload
della-cunningham -
Category
Documents
-
view
238 -
download
1
Transcript of Discovery of the Cell Robert Hooke (1665) –English scientist –looked at a thin slice of cork...
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-1600s) – 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
Cell Theory
• Two scientists, Matthias Schleiden and Theodore Schwann (1830s) expanded upon Hooke’s observation of “cells”
• Their observations in plants and animal cells have been summarized as the 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
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
three-dimensional 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
Eyepiece
Stage
Arm
Coarse AdjustmentFine Adjustment
Base
Light Source
Diaphragm
Stage Clips
Objective Lenses
Revolving Nosepiece
Body Tube
Source: http://www.biologycorner.com/microquiz/
Compound Light Microscope
Eyepiece – lens magnifies 10x
Stage – Supports the specimen slide
Arm – Always carry with one hand on the arm and one on the base
Coarse Adjustment – moves stage up or down to bring specimen into focusFine Adjustment – allows for precise focusing
Base – supports the scope
Light Source – provides the light that shines through the
stage
Diaphragm – controls the amount of light reaching the
stage
Stage Clips – hold the specimen slide to the stage
** Objective Lenses – magnify by 4x, 10x, 40x, or
100x
Revolving Nosepiece – holds and rotates objective lenses
Body Tube – supports the eyepiece and objectives
** Since the eyepiece had a magnification of 10x, the total magnification when using the 4x objective lens would be 40x. When using the 10x objective lens, the total would be 100x. When using the 40x lens, the total would be 400x.
Microscope: The Tube that Changed the World