Enhancement of Analytical
Thinking through Scientific
Investigations
Lesson 4-5
1
Structure of a plant cell
Cell wall
Cell membrane
Nucleus
Vacuole
Chloroplast
Animal cell vs Plant cell
2
Characteristics of cell membrane
Structure and Model
http://telstar.ote.cmu.edu/Hughes/tutorial/cellmemb
ranes/
3
Examination of plant cells
A matter of “ How ”
How can we really “see” the plant cells if
they looked “apparently transparent”?
We may need to make the cells
become “visible” ……
which is in fact very fundamental ……
4
Examination of plant cells
1.
2.
3.
4.
5.
By staining the cell wall?
By staining the cell membrane?
By replacing the water content inside the cell
with a colored solution?
How the cell “ingest” the color?
What is the expected observation using the
light microscopy? Do you think we can see cell
nucleus and organelles?
THINK ……
5
6
How to use a light microscope?
 Lower the stage or adjust the level of the objective so that the stage and the
objective are far from each other
 Turn objective lens to the one with the lowest power
 Place the slide (with specimen on it) onto the stage. The specimen should
be placed at the centre of the glass circle on the stage
 Look at the sample through the eyepiece. Try to get a focused image of
your sample using the objective lens with the lowest power by adjusting 1)
the coarse adjustment knob, then by 2) the fine adjustment knob
 After getting a focused image, if you want to pursue a higher power image,
turn the objective lens carefully to a lens with a high power (CAUTION: DO
NOT TURN THE ADJUSTMENT KNOB WHEN CHANGING THE POWER
OF OBJECTIVE, or you may either crack the slide, or lost focus of your
image which may become very difficult to focus).
Use the fine adjustment knob ONLY to focus the image
7
Microscope image
8
Examination of plant cells
Please read Part I
of the laboratory manual ……
9
Microscope image
Images from the microscope are laterally
inverted
Upside down
AND
Lateral inversion
10
Examination of plant cells
Magnification of image ……
Power of eyepiece x Power of objective
lens used for observation
Power of lenses are marked on the body of the lenses
If eyepiece has 10x and a 10x objective lens has
been used, magnification of the image should be
= 100x of original size
11
Examination of plant cells
Problem for lesson 4-5:
1
2
3
Examination of onion
cell under
light microscope
What
Why
How
12
Examination of plant cells
Please read Part II of the
laboratory manual ……
13
Examination of plant cells
1.
2.
3.
4.
How can you stain the onion cell?
Is treating the onion cell with alcohol important for
preparing the specimen?
Is it necessary to stain the cell? If yes, which is the
best stain among those you have used in this
experiment?
What did you find in your specimen? (Is it the
expected result?)
14
Examination of plant cells
Qualitative OR Quantitative
?
15