Download Cells and Microscopes

CELLS
PRINCIPLES OF THE CELL THEORY
The mid 1660s saw the advent of the microscope.
In 1665, Robert Hooke (an Englishman) saw a thin slice of cork (a plant material) with the use of a
compound microscope.
The cork was made up of thousands of tiny chambers which Hooke called cells.
• The Discovery of the Cell
– The mid 1660s saw the advent of the microscope.
– In 1665, Robert Hooke (an Englishman) saw a thin
slice of cork (a plant material) with the use of a
compound microscope.
• The cork was made up of thousands of tiny chambers
which Hooke called cells.
– Anton van Leeuwenhoek (a Dutchman) around the
same time looked at pond water with a single lens
microscope and found tiny organisms.
LIFE IS CELLULAR
– The Cell Theory
• Some after the previous discoveries, scientists were
sure that the cell was the basic unit of life.
• New discoveries: including all plants were made of
cells, all animals were made of cells, and new cells were
produced by the division of existing cells.
• The cell theory states:
– All living things are composed of cells.
– Cells are the basic unit of structure and function in living
things.
– New cells are produced from existing cells.
THE COMPOUND MICROSCOPE
• Microscopes produce magnified images of
structures that are too small to see with the
unaided eye.
• Light microscopes produce magnified images by
focusing visible light rays. Electron microscopes
produce magnified images by focusing beams of
electrons.
• Two problems exist
– How large can an object become
– How sharp can the image be
THE COMPOUND MICROSCOPE
• Light Microscopes
– These can produce clear images at magnifications
of 1000 times.
– Compound light microscopes allow light to pass
through the specimen and use two lenses to form
an image.
– Chemical stains , or dyes, can show specific
structures in the cells.
THE COMPOUND MICROSCOPE
• Electron Microscopes
– These can study objects smaller than 0.2 micrometers
which light microscopes cannot.
– They use beams of electrons, rather than light, to
produce images.
– These images are 1000 times more detailed than light
microscopes.
• Two types:
– Transmission electron
– Scanning electron
• Scanning Probe Microscopes
 Trace surfaces of samples with a fine probe
LIGHT MICROSCOPE
ELECTRON MICROSCOPE
THE COMPOUND MICROSCOPE
• Contains a combination of lenses
• The eyepiece lens has a magnification of 10X.
• Objective lenses are at the bottom of the body
tube.
• These can be rotated at the nosepiece.
– Have a 10X
– Have 40X or 43X
THE COMPOUND MICROSCOPE
• Carry with two hands, one beneath the base
and the other on the arm.
• Place gently on the table with the arm facing
you.
• Raise body tube by turning the coarse
adjustment knob.
• Rotate the nosepiece so that the 10X is in line
with the body
THE COMPOUND MICROSCOPE
• Look through the eyepiece and switch on the
lamp or adjust the mirror to see a circle of
light or field of view.
• Place the prepared slide on the stage so that
the specimen is over the center of the
opening.
• Look at the microscope from the side and use
the coarse adjustment knob so that the lowerpower objective almost touches the slide.
THE COMPOUND MICROSCOPE
• Look through the eyepiece and observe the
specimen.
• Do not lower the body tube when looking
through the eyepiece.
• Adjust the diaphragm to allow the correct
amount of light to enter.
• Rotate the nosepiece to change the
magnification.
THE COMPOUND MICROSCOPE
• Use the fine adjustment to bring the specimen
into focus.
• After use, remove the slide, put the low power
objective in place, clean everything with lens
paper.
PREPARING A WET MOUNT SLIDE
• Obtain a clean microscope slide and coverslip.
• Place the specimen in the middle of the slide
and add a drop of water with a pipette.
• Carefully lower the coverslip over the
specimen.
• Remove excess water with a paper towel from
the edge of the coverslip.
STAINING TECHNIQUES
• Obtain clean slide and coverslip.
• Place specimen in middle of slide.
• Place drop of water with pipette on specimen
and add coverslip.
• At the edge of the coverslip, add the stain .
• Using forceps, touch a small piece of lens
paper to the opposite edge of the coverslip
drawing the stain under the coverslip.