Enhancement of Analytical Thinking through Scientific Investigations

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Enhancement of Analytical Thinking through
Scientific Investigations
Lesson 4-5
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• Structure of a plant cell

Cell wall Cell membrane Nucleus Vacuole Chloroplas
t Animal cell vs Plant cell
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Characteristics of cell membrane

• Structure and Model
• http//telstar.ote.cmu.edu/Hughes/tutorial/cellmem
  branes/

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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
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Examination of plant cells

• 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
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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

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• Microscope image

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Examination of plant cells

• Please read Part I
• of the laboratory manual

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Microscope image

• Images from the microscope are laterally inverted
• Upside down
• AND
• Lateral inversion

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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
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Examination of plant cells
Problem for lesson 4-5

• Examination of onion cell under
  light microscope

What
Why
How
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Examination of plant cells

• Please read Part II of the laboratory manual

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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?)

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Examination of plant cells

• Qualitative OR Quantitative

?