Transcript tools of the biologist

Instruments
A. optical microscope:
 Uses Light rays,
which change direction when they pass
form one transparent medium to another.
Glass lenses ben light rays.
1. Simple: One lens, magnifying glass
2. Compound: uses two lenses. The
Objective lens magnifies the object first, and
then the eyepiece magnifies the second
image.
Parts and their functions

 Mechanical system: base, arc, stage, clips,
body tube, course adj, fine adj
 Optical system: Ocular &Objective (High
&Low power
 Light: a light source (mirror/lamp}.
 Diaphragm (regulates the light)
(disk/iris), condenser (concentrate the
light).
Parts of the microscope
 = Ocular X
Total magnification:
Objectives,
100x = (10x) X (10x)
Resolution: ability to show two
points as separate. Sharpness of an
image. Optical scopes are 500x
better tan the eye.
Optical Microscope

 Diaphragm: regulates the light
 Stained: Only certain parts absorb the stain to see
that part better. Can kill the cell.
Stereoscope

 Dissection scope/binocular scope): for studying
external structures. For opaque specimens.
Magnifies 6x to 50x. Provides a 3D image. Has an
ocular and objective for each eye.
 Phase contrast: Contrast among cell parts without
stains.
Electron Microscopes

 Electron microscopes: uses electrons, not light.
Electromagnets act as lenses to focus the electrons.
The more dense parts of the specimen don’t allow
the electrons to pass.
Advantages: increased magnification, increased
resolution.
Disadvantages: ultra thin specimens and can only
use dead organisms (vacuum)
TEM Transmission Electron
Microscope

 Magnify up to 250,000x Resolution: 10,000 times
greater then the eye. Specimen must be ultra thin.
May stain with atoms of heavy metal, which attach to
certain parts.
SEM (Scanning Electron Microscope):
Lower magnification. Surface detail. 3D. Electrons are
shot at it. The specimen is covered with gold, which
gets excited. The electrons that are excited are collected
on a screen.
Biological Techniques

 A. Fixing/Embedding/Staining
 1. material for microscopic examination must be thin
enough to let light pass through. Transparent.
 2. These methods prepare larger samples
(tissues/organs) for microscope examination.
 Fixing: hardens the specimen
 Embedding: put in paraffin
 Sectioning: sliced thin
 Microtome: does the slicing
Centrifugation

 Separates materials based upon their differences in
density (more dense will spin to the bottom.
materials to be separated are put in a liquid in a test
tube.
 Ultracentrifuge: high speed. Used for cell parts.
Spins at 40,000 to 100,00 revolutions.
Microdissection

 1. This is a dissection usually performed on
microscope specimen, such as cells.
 2. Some equipment used: microscalpel, microprobe,
microneedle, micromanipulator.
Tissue culture:
1. Living issue is grown (Cultured) in a solution.
2. Outside of the body. Gets all the nutrients it
needs. Used in medical research (Cancer, Aids)
Chromatography

 1. Chemical substances from a specimen are
separated/isolated using a solvent (dissolver)
 2. The degree of separation depends upon the
solubility of the materials in the mixture and
relative adherence to the paper used.
Electrophoresis
1. Material from a specimen are separated based
upon their electrical charge