Introduction to Lab 3--Microscopes and Cells
Objective of the Microscope and Cells Lab: The primary objective
of this lab is to learn to properly use the compound microscope
as a semiquantitative instrument. Once you can properly
use the microscope, there is a chance that you can use the microscope
to learn about small things like living cells. The lab final exam will have
a practical component wherein you will need to demonstrate that you can
properly use the microscope.
A) Bring your LAPTOP with you to lab so that you can access the
interactive version of these notes. You will go through this
outline online while actually handling your microscope.
B) Bring your Lab Manual (Symbiosis). You will use it in lab.
C) Bring a printed copy of the Study Sheet with you! The instructor
will stamp the printed copy that you bring at the beginning of the
class. The "stamp" will be worth 5 of the ten possible lab points.
D) Review the notes below, checking all hyperlinks, prior to coming to your lab section.
I. Microscope parts (be able to identify
all of the labeled parts)
A. microscope we will use
Labeled image
B. objective lenses
Labeled image A
Labeled image B
4X objective
10X objective
20X objective
40X objective
100X oil immersion objective
C. condenser lens assembly and iris diaphram
Labeled image
D. light source and limiting iris
Labeled image
E. mechanical stage control knobs
Labeled image
F. On-Off Switch
Labeled image
G. occulars and interpupillary distance
Labeled image
H. proper way to carry the microscope
II Using the compound microscope
A. proper way to carry the microscope from the cabinet to your bench.
B. clean the microscope lens if necessary
1. use LENS PAPER only
a. Do Not use KimWipes, Paper Towels
or facial tissue
2. one drop of distilled water on lens paper
3. gently wipe the occular, objective and
condenser lenses
C. plug the microscope into the outlet AND firmly push
the end of the power cord into the back of the microscope
D. rotate the 4X scanning objective
into the active position
E. use the coarse focus knob to raise the stage as
far up as it can come
F. turn on the light source
G. rotate the light intensity knob to a
comfortable level of illumination
H. check to be sure that the condenser
diaphragm is open as wide as it can be
in the 4X position and that the condenser assembly is in
its highest position relative to the stage
I. check to be sure that the light source iris is wide open
1. this iris needs to be wide open to have full
illumination when using the scanning objective
J. adjust the interpupillary distance for your eyes
K. look through the occulars and adjust the light
intensity using the variable light control knob in the base
L. clean your slide and place it onto the
stage such that it is
held in place with the spring loaded retaining clip
-closeup of the retaining clip
M. with your head to the side looking down
at the stage, use the mechanical stage
control knobs to center the object to be
viewed in the middle of the hole in the stage
N. while looking through the occular lenses slowly
LOWER the stage with coarse focusing knob until
the object to be viewed comes into focus
-NOTE that the lens is well above the slide
-CHECK that the objects that you are viewing actually on the slide
by slightly turning the mechanical stage control knobs. When
you do this, the objects should move as well.
O. use the fine focusing knob to
get the sharpest focus
O. while looking through the occulars, CENTER
the object to viewed in the exact middle of
the field of view with the mechanical stage
control knobs
P. with your head to side watching the
objectives and stage, rotate the nosepiece
such that the low power (10X) objective
swings into the active position
-NOTE that the 10X is much closer to the slide
-This will ALWAYS be the case with the
10X objective
Q. return the lowest condenser lens to the
active light path
R. while looking through the occulars, adjust the
light intensity with the variable light control in the base
S. while looking through the occulars,
slowly adjust the focusing knob until
the object to be viewed comes into sharp focus
-CHECK that the objects that you are viewing actually on the slide
by slightly turning the mechanical stage control knobs. When
you do this, the objects should move as well.
T. CENTER the object in the exact middle
of the view of view
U. with your head to side watching the
objectives and stage, rotate the nosepiece
such that the hi power (40X) objective
swings into the active position
-NOTE that the lens is VERY CLOSE to the slide
-This will ALWAYS be the case with the
40X objective
V. while looking through the occulars,
slowly adjust the fine focusing knob until
the object to be viewed comes into sharp focus
-It is best not to try to use the coarse focus
knob with the 40X objective
-CHECK that the objects that you are viewing actually on the slide
by slightly turning the mechanical stage control knobs. When
you do this, the objects should move as well.
W. center the object in the exact middle
of the view of view
III Measuring the field of view with a microscope
A. find a prepared slide that has a clear ruler
taped to the top side.
B. place a clear ruler slide over the hole
on the stage
C. focus on the larger black lines that indicate the
millimeter mark with the scanning objective
so you can clearly see the 1 mm lines
D. move the line of millimeter marks until they
stretch across the widest part of the field of view
E. count the millimeter marks to determine the
diameter of the field of view in mm
F. calculate the diameter of the field in micrometers
1 meter = 1,000 millimeters = 1,000,000 micrometers
1 mm = 1,000 um
0.5 mm = 500 um
0.25 mm = 250 um
G. repeat steps B, C, D for the low and high
power objectives
IV Making a wet mount of an Elodea leaf
A. place one SMALL drop of water in the center
of clean microscope slide
B. remove one Elodea leaf and place it on
the drop of water
-NOTE: if the leaf is large and doesn't lay flat,
cut off a small section of the leaf to view and discard
the larger section (the sample must lay flat on the
microscope slide)
C. hold a coverslip at a 45 degree angle with one
edge close to the drop of water
D. lower the coverslip onto the Elodea leaf by
reducing the angle, being careful not to trap bubbles
E. the coverslip should lay flat on the sample
-NOTE: if necessary, push down gently to
flatten the coverslip against the slide
F. remove any excess water that is exposed on
any part of the slide or coverslip using small pieces of paper towels
-NOTE: with a good wet mount, there should be no
chance of moving liquid from the slide to any part of
the microscope (objectives or stage)
G. cartoon of a good wet mount
H. cartoon of a bad wet mount
V Making a wet mount of highly mobile protists (eg: Paramecium)
A. squeeze about 1/2 drop of ProtoSlo (a very
viscous methylcellulose solution) onto a
clean microscope slide
1. spread the ProtoSlo around with a toothpick
2. ProtoSlo is made from VERY long soluble
fibers that entangle Paramecium
and slow it down so that you can follow it
with your high power objective
B. use a eye dropper to pickup a tiny amount of
the detritis at the bottom of the
Paramecium container
C. place about 1/2 drop of the Paramecium
media next to the ProtoSlo
D. use a toothpick to gently mix the two
solutions together
E. position a coverslip as you did with the
Elodea slide
F. remove any excess water and/or ProtoSlo
G. NOTE: Do not let ProtoSlo get on the
objective lenses or the stage. ProtoSlo
becomes very sticky. When on the lenses,
ProtoSlo makes the lenses unuseable.
When on the stage, ProtoSlo makes the
slides stick so they can't be moved
with the mechanical stage.
VI Finding Paramecium or other highly mobile cells
A. place your wet mount on the stage
B. with your head to side, locate a piece of
detritus and center it the middle of the
hole in stage
C. use the scanning objective to locate the
target piece of detritus and then center the
detritus in the middle of the field of view
D. look for Paramecium at low and high power
as described above
VII Organization of Cells
A. unicellular
1. all functions of life handled by one cell
2. Ameoba
3. Trichonympha
4. Chlamydomonas
5. Paramecium
B. colonies
1. consistent, predictable clusters of
cells of the same species
a. not physiologically connected
b. cells can be separated and all are viable
2. Protococcus
3. Scenedesmus
C. complex colonies
1. consistent, predictable clusters of
cells of the same species
a. are physiologically connected
b. cells specialization occurs
c. more difficult to separate cells and
maintain viability
2. Volvox
D. multicellular organisms
1. large numbers of cells
a. great specialization of cells
b. difficult or impossible for cells to
exist alone without other cells
of the organism
2. Elodea
3. Homo sapiens
VIII Lab activities in Symbiosis--"Microscopes and Cells"
A. read Exercise 1, 2 and 5. Skip Exercises 3 and 4.
B. do exercise 2 but use the outline above
C. skip exercise 3
D. skip exercise 4
E. do exercise 5 with the organisms provided
-Paramecium
-Amoeba Demonstration Only
-Volvox
-Scenedesmus
-Elodea
-yeast
-human cheek epithelial cells
VIII Assignment
A. print the assignment BEFORE coming to lab (stamp will be worth 4 points)
B. hand in the assignment at the end of the lab (completed assignment 5 additional points)
C. assignment will be returned by next week
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