Cells
Organelles
CELL
• The basic unit of structure &
function in living organisms
Anton Van Leeuwenhoek
1632-1723
Was a merchant that ground up glass to
make lenses
•Invented microscope
•Made over 500 in his lifetime
•1st person to examine bacteria
Van Leeuwenhoek’s sketches of a nerve
Robert Hooke
• 1635-1702
• Used Van Leeuwenhoek’s microscopes
• Named cells after looking at cork
Robert Hooke’s Cork
Robert Brown
• 1773-1858
• Discovered the nucleus
in plant cells (1833)
Matthias Schleiden
• 1804-1881
• Discovered all plants
are made up of cells
(1838)
Theodor Schwann
• 1810-1882
• Discovered that all animals
are made up of cells (1839)
Rudolph Virchow
• 1821-1902
• Proposed that all cells come from preexisting cells (1855)
The Cell Theory
The cell theory states:
A.
All living things are composed of cells
B. Cells are the basic units of structure & function in
living things
C. All cells come from preexisting cells
Janet Plowe
• Demonstrated that the cell membrane is a physical
structure (1931)
Lynn Margoulis
• Proposed that certain organelles were once freeliving organisms themselves (1970)
Parts of Microscope
Nosepiece
Ocular
High Power Objective
Arm
Low Power Objective
Scanning Power Objective
Stage
Course Focus
Fine Focus
Stage Clips
Diaphragm
Base
Light (illumination)
Compound light Microscope Parts & Fxn’s
• Occular – viewing eyepiece
• Coarse adjustment – Rough focus
• Fine adjustment – Fine focus
• High power objective (400X)
• Low objective (100X)
• Scanning objective (40X)
Compound Light Microscope Parts & Fxn’s
• Stage – holds slide up against stage clips
• Stage clips – holds slide down on stage
• Diaphragm – controls amount of light entering slide
• Lamp – light source
This is an air bubble
under the microscope!!!
Power of magnification
• The relative enlargement of the specimen when
seen through the microscope.
• The power of magnification can be calculated by
multiplying the power of the eye piece lens by the
power of the objective lens.
Inversion
• The reversal of the specimen image by the
microscope lenses.
• A specimen that appears upside down when being
viewed is actually right-side up on the slide.
•
Moving the specimen to the right causes its image
to move to the left likewise, moving it down causes
it to move upward.
Working distance
• The distance between the front of the objective
and the top of the cover glass on the slide.
• The higher the magnification the smaller the
working distance.
• DO NOT USE THE COARSE ADJUSTMENT
UNDER HIGH POWER!!!
Resolution
(Resolving Power)
• The shortest distance between two points or lines
at which they are seen as two, rather than a single
blur.
Depth of focus
• The thickness of a specimen which
may be seen in focus at one time.
Objectives
• Our microscopes have three objectives mounted
on a revolving device known as a nosepiece.
•
Engraved on the objective is its power of
magnification.
• The longer the objective the more power of
magnification.
Diaphragm
• A device under the stage of a microscope that can
regulate the amount of light reaching a specimen.
Power of Magnification
• Definition - The relative enlargement of the
specimen when seen through the microscope.
• Power of magnification = (Power of the eyepiece
lens) X (Power of the objective lens)
Rules for Handling the Microscope
• Always carry the microscope with one hand under the
base and the other grasping the arm.
• Keep both eyes open when looking through the
eyepiece.
• Keep the stage clean and dry.
• Do not remove parts of the microscope.
• Use only lens paper when cleaning lenses.
Rules for Handling the Microscope
• Always begin focusing with the lowest power
objective.
• Always look from the side when changes lenses
• After completing your work, place the microscope on
the lowest power objective.
• Always return the microscope where you found it & as
you found it
Modern Microscopes
Electron microscopes – capable of revealing details as
much as 1000 times smaller than those visible in light
microscopes. (Two types -TEM & SEM)
TEM – can explore cell structure and large protein
molecules.
Downside – the specimens have to be sliced thinly
T.E.M.
Transmission Electron Microscopy T.E.M.
Modern Microscopes
S.E.M. – Scanning electron microscopes –
specimens do not have to be cut thinly – a
beam of electrons scans over the specimen.
S.E.M.
S.E.M.
Magnification
Prokaryotic & Eukaryotic Cells