1 E nhancement of A nalytical T hinking through S cientific I nvestigations Lesson 4-5

2 Structure of a plant cell Cell wall Cell membrane Nucleus Vacuole Chloroplast Animal cell vs Plant cell

3 Characteristics of cell membrane Structure and Model branes/

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 ……

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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: WhatWhyHow

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 ?