Laboratory 2
Zoology 1121
Microscopy / Cell Theory
I. Microscopy
- 2 important factors in microscopy
1. Magnification: is how much larger the object appears compares to its
real size
2. Resolving power: is a measure of the clarity of the image, or the minimum
distance two points can be separated
and still be distinguished as two separate points. (ex, a star in sky w/
unaided eye might be twin stars with a
telescope)
- most detail with light microscopes is 0.2 micrometers , size of small
bacteria or mitochondria
- about 1500x
-Discuss 4 types of microscopes; different uses in hypothetical situations
1. Simple 1 lens
2. Compound 2 lenses:
ocular x objective
3. Dissecting (stereomicroscope)
less magnification than compound but for objects that are too large to
be viewed
with compound. Both transmitting and reflected light
4. Scanning Electron Microscope
[SEM] beams of electrons views mainly by computer and photograph. Key
is 2nd
set of electrons . 2-D image. 200,000x
5. Transmission Electron
Microscope [TEM] - 1 beam of electrons passed at a organism. Not
an 2D image , its 3D
- Units of measure is the micrometer
- handling of microscope : NEVER SLIDE
- how to clean lenses dry paper only
- never focus upwards
Terms
1. Ocular lens a.k.a. eye-piece, usually a 10x magnification
2. Objective lens provides the resolving power , mounted to the revolving
nosepiece
3. Stage slide-mounts go on here
4. Condenser - funnel of light
5. Iris diaphragm -controls amount of light passing through the condensor
6. Coarse focus
7. Fine focus
9. Field of view size: with ruler, number of marks straight across
the widest part of the field x 1000: 4x, 10x, 40x
10. Resolving power- the formation of an image in which the details
are distinctly distinguished
11. Nosepiece objective piece rotates on this
12. Parfocal focused under low power are also in focus under the
higher magnification
13. Depth of Focus - is the vertical distance that remains in focus
@ any particular point
14. Focal plane - the plane of focus passing through a specimen.
Hitting the c/f adjustments raises or lowers this
- together the ocular times the objective = magnification
- 10x = ten times the original size
- pointer eye- the eye-piece rotates to get the pointer
- the students should write in their lab manuals which of the strands
of thread is on top, which is in the middle, which is
on the bottom.
- The TA will go around the room to check each students notation and
to confirm their identification or to get them to look
more closely
- The size of fields at the different magnifications should be noted
in their books
- The student will use these field sizes in later lab
- Lab Microscope exercise
- Stress why we are doing these exercises
1. letter e- slide to learn to focus, locate things in microscope
field, and illustrate how things move when being viewed
under magnification (p209)
2. Crossed thread slide: to evaluate the depth of field
3. Ruler Slide: to enable students to measure the size of the field
at each magnification which will allow for estimations
of cell/object size in later
labs
4. Have students fill out table on p. 210 (top-right) We use this data
in later labs
II. Cell Biology
- The main objective of this lab is to understand the components of
the Cell Theory and to understand what occurs during the
Cell Cycle
- Cytology study of cells, importance of cellular study
- cells are basic units of structure and function
- similarities among cells [conserved evolution]
- organelles, enzymes, DNA, etc
- replication also is same across different kingdoms: in amoebae, plant,
animalia
- conserved over evolution- similar cellular level but see the differences
at the organismal level
- increase in specialization : (cell tissue organ)
- selective use of genetic material
Cell Theory
1. a cell is the fundamental biological unit
2. all living things are composed of cells
3. all cells come from preexisting cells
Terms
1. plasma membrane outer limiting membrane that encloses a cell
2. nuclear membrane outer membrane that holds in the DNA and other
nuclear structures
3. nucleolus site of ribosomal RNA [rRNA] production
4. chromatin association of DNA and proteins (ex, histine binding
complex); site of mRNA production
5. cytoplasm the cellular matrix that contains all the other functioning
units of the cell (ex, ER, Golgi App, etc)
Lab Cell Exercises
- students should note we will progress with complexity
1. Sea Star Egg (fig. 2.2a)
- students should find an
egg and label all of its structures
- have students estimate
its size and its components
2. Human Epithelial cell
- Give procedures for making
a wet-mount
- No Vaseline, just place
cover-slips directly on slide
- Actually better since
it will flatten cells for better observation
- Stress importance of using
very little methylene blue stain
- Have students draw and
label a cheek cell in space B fig 2.2
- Estimate the cells size
3. Specialized Cells nerve cell
- observe cell
- estimate size and label
its components in space 3 fi 2-3
- discuss how form of cell
will always reflect its function
- this exercise is to get
the students thinking about how form of cells reflect the function of the
cell.
III. Cellular Reproduction
Whitefish blastula
Mitosis cell count experiment is designed to illustrate that cells
stay in the various stages of the cell cycle for differing
amounts of time and that
the amount of time spent is a reflection of what is going on during the
cell during that stage
1. Introduction
1. Cell Cycle-
2. Interphase: between mitosis creates a full complement subcellular
cytoplasmic organelles as well as a second
set of chromosomes
- Nuclear membrane is actually
intact
- G0, G1, S, G2
3. Mitosis begins with the separation of the duplicated chromosomes
- Meiosis sex separation
4. Physical events of mitosis [fig 2-10]
- interphase, prophase,
metaphase, anaphase, telophase
5. Purpose of mitosis
- Why it occurs- for separating
of nuclear material
- Where it occurs
6. Blastula - early embryonic stage of a living organism
- the students will have
to count the various stages. This exercise constitutes another type
of observation that
requires careful attention to what is on the microscope stage.
- The students also need
to estimate the size of the blastula cells and record the size in their
books
- many cells replicating
7. Cancer cell: wildly replicating cell
Terms
1. mitosis
2. chromosomes
3. cell cycle vs. mitotic cycle
4. interphase
5. prophase
6. metaphase
7. anaphase
8. telophase
9. cytokinesis
Exercise 6
- find all stages of mitosis
on their slides
- reinforce findings with
the video scope
4. Propose: how long does stage of mitosis take?
- Find answer using blastula
- We assume 24 hrs for cell
cycle, 1 hr for mitosis
- Enforce the logic behind
this exercise
- Make sure they understand
how the number of cells counted in each stage relates to the amount of
time spent
in that stage.
- High power objective with
fixed field of view, have students count the number of cells in each stage
- Accumulate class data
on board and have students enter data ala the computer
- Calculate means and standard
deviations on board
5. Collection of Numerical Data
- Collect at least 5 data
points. Record data for future lab.
- Combine on the board
- students know this
as average, but big science name is called mean
- Mean Examples
dont tell you much, so use standard error of the mean, which measure
cluster around the mean
Ex 1.] 4 + 5+ 6 =15 Ex 2. 12 + 1 +2 =15
Mean: 15 / 3 = 5 Mean: 15/3 = 5
- Standard Error of the
Mean [SEM]
- use MSExcel
- Summation [=SUM(letter#:letter#)
- Mean [=AVERAGE(R2:R26)]
- Standard deviation [=STDEV(R2:R26)]
- make graphs from data
- calculate amount of time
a cell spends in each stage of cell cycle
- Again: make sure they
understand how the number of cells counted in each stage relates to the
amount of time
spent in that stage.
Important terms:
ocular lens
objective lens
stage
condenser
coarse focus
fine focus
depth of field
field of view
plasma membrane
nuclear membrane
nucleus, nucleolus
chromatin
cytoplasm
mitosis
chromosome
cell cycle vs. mitotic cycle
interphase
prophase
metaphase
anaphase
telophase