Unit 4: Microscopes,
Structure and Function
of Cells
Microscopes -The Cell Theory
HONORS BIOLOGY
Monkemeier 2014
History of Knowledge
 1665:
 1673:
 1833:
 1855:
 1857:
 1897:
Robert Hooke
van Leeuwenhoek
Schleiden and Schwann
Virchow
Discovery of Mitochondria
Discovery of Golgi Apparatus
Timeline of Events in Perspective
The Cell Theory
 All
living things are composed of
one or more cells.
 The cell is the basic unit of
structure and function of
organisms.
 Cells come from the reproduction
of preexisting cells.
Microscopes


1590:Zacharias
Jansen and the
first compound
microscope
Their first microscopes
were more of a novelty
than a scientific tool
since maximum
magnification was only
around 9x and the
images were somewhat
blurry.
Van Leeuwenhoek


Anton van
Leeuwenhoek (16321723), a Dutch draper
and scientist, and one
of the pioneers of
microscopy who in the
late 17th century
became the first man
to make and use a
real microscope.
First to view
Protists, Bacteria,
Plants, Yeast.
Modern Microscopes
 Compound
Light
Microscope
 Scanning
Electron
Microscope
 Transmission
Electron
Microscope
Resolving Power
–the ability of the
microscope to
produce separate
images of two
closely spaced
objects. Produce
clear, crisp image
 Magnification –
the enlargement of
the image.

Microscope Comparison
The Resolving Power of a microscope is
limited by the wavelength radiation used
to view the sample.
 Light used in microscopes has a
wavelength of 400 – 600 nanometers.
 Increased resolution requires smaller
wavelength.
 Beam of electrons used in electron
microscopes has a wavelength of less than
1 nanometer!

WHY does Wavelength of
Radiation Matter?
 Refraction
 The
beam of electrons will not
have as much refraction as
visible light.
 Refraction is the bending of
“light” as it passes through a
lens (moves from one medium to
another)
Comparison of Microscopes: Light
 Uses
beam of visible light to produce
image.
 Image produced is true to color as
the original specimen.
 Specimen can be live.
 Can magnify up to 1000x
 Can see cells.
Comparison of Microscopes –
Transmission Electron Microscope
Uses a beam of electrons to produce
image.
 Image produced is called micrograph and
it is in black and white.
 Can magnify up to 200,000x
 Specimen must be sliced extremely thin.
Distortion can occur due to this.
 Can see cross-sectional area.
 Can see organelles.

TEM
Comparison of Microscopes:
Scanning Electron Microscope
 Uses
a beam of electrons to produce
image.
 Image produced is a threedimensional surface view.
 Image produced is black and white
 Can magnify up to 100,000 x
 Specimen must be coated with gold
and placed in a vacuum.
SEM
Your Turn
Use
your notes to construct a
chart which compares
Compound Light Microscopes
to Transmission Electron
Microscopes and Scanning
Electron Microscopes!
Comparison Chart
Microscope
Compound
Light
Microscope
Transmission
Electron
Microscope
Scanning
Electron
Microscope
Source
of
Image
Type of
image
Magnification
Preparation of
Specimen
Special
Concerns
Limitations