Download Origin of Cells and the Cell Theory

Cells and the
Origin of Cell
Theory
History of the Cell Theory
• Before microscopes, belief in
supernatural causes of
diseases
• Could not see
microorganisms
• What branch of biology?
• Cells = basic units of living
organisms
Microscopes
• Originally a hand lens to view
quality of cloth
• Anton van Leeuwenhoek
(mid-1600s) first to examine
water under microscope
• Credited with development of
light microscope
Anton von Leeuwenhoek’s
Microscope
Improvements
• Compound light
microscope- series of lens
to magnify objects (1500x)
• Robert Hooke used one to
observe cork magnified
30x
• Observed small geometric
shapes
• Dubbed these cells
(resembled monk rooms)
Hooke’s Microscope
Cell Theory
• 1830’s German scientist
Matthias Schleiden
realized that plants made
up of cells
• Theodore Schwann
made same
determination of animals
• = Cell Theory
• Many resources
(including your book)
give only credit to
Scleiden and Schwann
• Original third tenet was
spontaneous generation
• Rudolph Virchow "Omnis cellula e cellula”
Cell Theory
• All organisms are
composed of one or
more cells
• The cell is the basic unit
of organization of
organisms
• All cells come from
preexisting cells
Recent Developments
• 1940’s were able to use
beam of electrons
instead of light
• 500 000x
• Electron microscope
• Scanning Electron
Microscope
• Transmission Electron
Microscope
Scanning Electron
Microscope
• SEM
• Electrons
are
reflected off
the surface
of the
specimen
• 3D shape
• http://micro.magnet.fsu.edu/
primer/virtual/virtual.html
• http://www.mos.org/sln/SEM
/gallery.html
Transmission Electron
Microscope
• TEM
• Allows to see
inside of cell
• Electrons pass
through
instead of light
• http://nobelpriz
e.org/physics/e
ducational/micr
oscopes/tem/
Size Comparison
Prokaryote vs. Eukaryote
• With the invention of
microscopes, scientists
could see two groups of
cells
• Prokaryotes
• Eukaryotes
Prokaryote
• 1-10 m in diameter
• NO membrane-bound
organelles
• 1 circular DNA molecule
located in nucleoid
region
• Plasma membrane,
cytoplasm & ribosomes
• Most have a cell wall
(peptidoglycan)
• May have a
polysaccharide capsule
–Ex. bacteria &
cyanobacteria
Prokaryotic Cell
Eukaryote
• 10-100 m in diameter
• Nucleus & other membranebound organelles
• 2 or more linear DNA
molecules located in
nucleus
• Plasma membrane,
cytoplasm & ribosomes
some have a cell wall
(cellulose or chitin)
Ex. plants, animals, fungi,
protista
Animal Cell
Anima
l Cell
Plant Cell
QUESTIONS?????