1

Enhancement of Analytical Thinkin

g through Scientific Investigations

Lesson 4-5

2

Structure of a plant cellCell wall

Cell membrane

Nucleus

Vacuole

Chloroplast

Animal cell vs Plant cell

3

Characteristics of cell membrane

Structure and Model

http://telstar.ote.cmu.edu/Hughes/tutorial/cellmembranes/

4

Examination of plant cells

How can we really “see” the plant cells if they looked “apparently transparent”?

A matter of “ How ”

which is in fact very fundamental ……

We may need to make the cells become “visible” ……

5

Examination of plant cells

1. By staining the cell wall?

2. By staining the cell membrane?

3. By replacing the water content inside the cell with a colored solution?

4. How the cell “ingest” the color?

5. What is the expected observation using the light microscopy? Do you think we can see cell nucleus and organelles?

THINK ……

6

7

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

8

Microscope image

9

Examination of plant cells

Please read Part I

of the laboratory manual ……

10

Microscope image

Images from the microscope are laterally

inverted

Upside down

AND

Lateral inversion

11

Examination of plant cells

Power of eyepiece x Power of objective

lens used for observation

Magnification of image ……

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

12

Examination of plant cells

Examination of onion cell under light microscope

Problem for lesson 4-5:

1 2

3

What Why How

13

Examination of plant cells

Please read Part II of the laboratory manual

……

14

Examination of plant cells

1. How can you stain the onion cell?

2. Is treating the onion cell with alcohol important for preparing the specimen?

3. Is it necessary to stain the cell? If yes, which is the best stain among those you have used in this experiment?

4. What did you find in your specimen? (Is it the expected result?)

15

Examination of plant cells

Qualitative OR Quantitative

?