Download Biological Tools

Biological Tools
Microscopes
Introduction
• Most widely used tool in biology
• Allows us to see things we can’t
see with the naked eye.
• The science of Microbiology
started with the invention of
microscopes
Magnification: An increase in an objects apparent size
mag·ni·fi·ca·tion (m g n -f -k sh n) n.
1. The act of magnifying or the state of being magnified.
2. a. The process of enlarging the size of something, as an optical image.
b. Something that has been magnified; an enlarged representation,
image, or model.
3. The ratio of the size of an image to the size of an object.
Resolution : The power to show details clearly. The fineness of
detail that can be distinguished in an image
VS
As a general rule, magnification and resolution are
inversely related. That is as magnification increases,
resolution decreases.
Simple Light Scopes
• Simple Light Scopes use a single
piece of curved glass (lens) to
produce a larger image of a
specimen
– Refraction = bending of light
causes distortion/enlargement
– Most common example =
Magnifying Glass
– Again, as magnification increases,
resolution decreases
Compound Light Scopes
• Contains two lenses:
1. Ocular Lens (Eyepiece)
2. Objective Lens
Total Magnification = Ocular x Objective
X
Light Scopes have limits – can reach about
2,000X magnification
Parts/Usage of Microscopes
Parts/Usage of Microscopes
• Eyepiece (Ocular Lens)
• Usually contains a 10X
lens
• Arm: curved or solid
back of the microscope
• Helps support the
weight,
• This is where you hold
the scope when you are
carrying it!
• Body Tube: Proper
space between eyepiece
and objective lenses.
• Allows for proper
resolution (clarity)
• (Revolving)
Nosepiece: rotating
plate that attaches
multiple objective
lenses.
• Allows you change
objective powers.
• Objective Lenses: 2nd set of
lenses closest to the
specimen.
• Many scopes have multiple
lenses with different powers
(4X, 10X, 40X)
• Lower power – shorter lenses
• Higher powers – longer
lenses
• Stage: platform to hold
slides
– Some have stage
clips to hold the slide
– Some have
mechanical stages
• Course Adjustment
Knob: The larger of the
two focusing knobs
• Used for focusing in
lower powers – makes
large scale adjustment
by moving the stage up
and down.
• Never use under high
power objectives !
• Fine Adjustment
Knob: The smaller of
the two focusing
knobs
• Used for focusing in
higher powers –
makes microscopic
adjustments. (you
won’t be able to see
the stage move)
• Light Source:
Located under the
stage.
• Designed to run a
beam of light through
the specimen to be
magnified
• Old scopes used
mirrors to reflect light
up through the
stage.
• Diaphragm: rotating
disk on the underside of
stage (hard to find)
• Controls how much light
passes through
specimen
– Thin transparent
specimens require little
light
– Thick colorful specimens
require a lot of light
• Base: bottom of
scope
• Used to support the
weight.
• Also have one hand
underneath when
carrying !
Proper Care
•
•
•
•
•
Always use two hands when carrying
Keep the scope close to your belly !
Keep scopes away from the table edge
Never drape the cord where someone can walk
Avoid moving the scope around on the desk (use the
revolving eyepiece)
Specimens
• Specimens should be rather thin – light must be
able to pass through them.
• Stains or chemicals are sometimes used to
highlight or darken certain structures for easy
viewing
UNSTAINED CHEEK
CELLS
STAINED CHEEK
CELLS
Other Biological Tools
Stereomicroscope/Dissection Scope
•
•
•
•
Light Scope
3-D Images
Low Magnification
Used in dissections, with
insects, and small living
things/structures
Electron microscopes
• Most Powerful scopes
• Uses electrons
• Resolution no longer a problem with
high magnification
• Several Types (TEM,SEM)
Knoll and Ruska
in 1947
How do electron scopes work?
In an electron microscope…
The light source is replaced by a beam of very fast
moving electrons.
The specimen usually has to be specially prepared
and held inside a vacuum chamber from which the
air has been pumped out (because electrons do not
travel very far in air).
The lenses are replaced by a series of coil-shaped
electromagnets through which the electron beam
travels.
In an ordinary microscope, the glass lenses bend
(or refract) the light beams passing through them to
produce magnification. In an electron microscope,
the coils bend the electron beams the same way.
The image is formed as a photograph (called an
electron micrograph) or as an image on a computer
screen.
Transmission Electron Microscope
TEM
• Most powerful scope
(1,000,000X and up)
• Image projects onto a
photographic plate
• Used to see internal
cellular structures
• Samples must be
treated with heavy
metal stains (kills
living cells)
TEM Micrographs
(Notice they are 1D or flat images)
Scanning Electron Microscope
SEM
• Produces a 3 dimensional image
• Specimens aren’t sliced but are
sprayed with a fine metal coating
• A beam of electrons is passed over
the surface of the metal coating to
emit a shower of electrons
• Showered electrons are projected onto
a fluorescent screen or photographic
plate
• SEM's produce greatly magnified image
of surface details of specimens
• Can magnify up to 100,000 times
• Can not be used to view living
specimens
SEM Micrographs
ANT
Bacteria Cells Light Scope vs. SEM
Honeybee Head with pollen on it
Leukemia (cancer) Cells on left
Normal Bone marrow cells on right
Microtome
• Used to slice extremely thin
microscope specimens
• Biopsy placed in wax to slice
Centrifuge
• Used to separate materials by high
speed spinning - Centrifugation
Parts of a mixture will
separate based on size
and density
Blood Centrifugation
Apheresis Donation:
1. Blood drawn & centrifuged
2. Plasma and/or platelets removed
3. Red Blood Cells returned to donor
An Apheresis Centrifuge
Chromatography
• Separation technique of chemicals
• Based on dissolving rates (solvents)
Gel Electrophoresis
• Used to separate large
molecules into smaller
pieces
• Primarily Based on
charge
• Common with
DNA/Forensics