BIO150-3 / Report Lab 2: Microscopy and Cell Structure

Lab 2: Microscopy and Cell Structure

 Aim:To observe some different cell types and the organelles they contain. To see firsthand the major differences between plant and animal cells which I will learn about in the BIO 100 lecture course next week. 

Purpose:To become familiar with the use of both compound and dissecting microscopes and to use them to observe cells and biological matter at both the microscopic and macroscopic level. All organisms consist of one or more cells and specific stains an be used to highlight some of the organelles and structures they contain. 

Materials: 

Plant cell materials (onion/potato/weeds from teacher’s garden)

Animal cell materials (cured fish eggs)

Plastic micro-centrifuge tube in which has water fleas in.

Stains (solutions of Iodine/ Methylene blue/ Safranin/ EosinY/ Phenol red)

Salt and water

Tools:

Compound microscope (single eyepiece)

Dissecting microscope (stereo eyepiece)

Side glass and cover glass for my own sample preparation

A pair of scissors for chopping

Electric scale

A small case to measure the salt and water.

Dissecting kit

Dropper pipette

Tweezers

Lamp

Camera station that is attached to either the light or dissecting microscope

 Procedure: 

1. Rescued the microscopes from inside or under their own box or cover. 

2. Set the lights into the compound microscope, adjusted its focus using the practice slides and saw how it looks like.         

3. Cut the onion into a little piece, and stripped a thin inside skin off.       

4. Put the skin on the slide, dropped 1 or 2 drops of water on it, and covered it by a cover glass.      

5. First just looked at it using the compound microscope without staining it. Tried different objective lenses in this process. 

6.  When I could find the cell walls and nucleus in each one of them, then I took pictures of them using the computer.      

7.      I stained the onion cell with the Methylene blue using the Dropper pipette and observed how it looks like.    

8.      Then next, I cut the sliced potato into very thin, made the slide with it, and observed the slide with the Compound microscope.

9.      I added the EosinY in it, and abserved it again.

10.   I cought water fleas from the plastic micro-centrifuge and made a slide with it carefully putting a cover glass on it.     

11.  Observed the slide with the Compound microscope and took its picture using the computer. 

12.  Observed the fish egg using the Dissecting microscope, and saw how it looks like.      

 

13.  Observed the dragon fly using the Dissecting microscope, and saw how it looks like.

 

14.  Made the onion slide again, observed it without stain it. Then I added the salt water (salt: water= 1:6 g) slowly with the dropper pipette and observed how it changes. 

Results: 

Sample Slide: When I looked at the sample slide, I could see small letter “e” on it.

 

Onion Cell: When I looked at the slide on which I put the onion inner skin, even though I didn't stained it, but I could see its cell walls and nucleus in each one of them.

When I stained the onion cell with the Methylene blue using the Dropper pipette and observed it, I could see the nucleus in each one of the cell walls. 

Potato Cell:  I observed the potapo cell with the Compound microscope, and then I noticed that it looks quite different from the onion cell, because there were a lot of bubbles on or in the each cell wall. 

After this, I added the EosinY on it, and observed it again.

Then I could see the bubbles and cell walls more clearly.

 

Water Fleas: I made a slide with some water fleas and observed how they look like. It looked very much different from plant cells. They didn’t have cell walls, and I could see many small yellowish round things in it. I also could see it’s moving because it was still alive.     

 

Fish Egg: When I observed the fish egg using the Dissecting microscope, I only could see big shiny red fish egg. I couldn’t really see any cells in it.

Dragon Fly: I observed the dragon fly using the Dissecting microscope, and noticed that it is coved by small thin hairs all over its body. I could see the very detail but cell using the dissecting microscope.

 

Plasmolysis: I added the salt water (salt: water= 1:6 g) slowly into the onion slide with the dropper pipette without staining. As soon as I added the saltwater, I could see the change of the plasma membranes. They shrunk very rapidly separating from their cell walls. This change happened within about 20 -30 seconds. I took its video.

Control(Before adding the salt water) 

The result of the plasmolysis (after adding the salt water)  

Conclusions: I could observe many plants and some organic cells using the both compound and dissecting microscopes. I think I could observe cells and biological matter at both the microscopic and macroscopic level. I also could observe some different cell types and the organelles they contain. I could see firsthand the major differences between plant and animal cells. All organisms consist of one or more cells and I used some specific stains to highlight some of the organelles and structures they contain, such as Nucleusｓ. .

Comments/ Discussion: When I looked at the fish egg using the dissecting microscope, I could see the shiny red stuff in it. I remember some students tried to put fish egg into the salt water, I wonder what happened to them after that. I guess that it might be shrunk because of the osmotic pressure.

I have studies about the plasmolysis before at my high school, but I don't remember if once the plasmolysis happened, there is any ways to make it back to the original place or not.

 Answer to Questions: 

1)      If you increase the magnification, what happens to your field of view?

-If I increase the magnification, the field of view decreases.

 

2)      What is the difference between the conventional microscope and the dissecting microscope? Why did you choose the microscope you did for the samples you looked at?

-A dissecting microscope has a lower magnification than a compound microscope. A dissecting microscope has a bigger work area so you can use it to magnify and still move around what ever you’re looking at. A compound microscope would be used to look at cells that you could not see with out intense magnification you would have to use a microscope slide for whatever you wanted to look at.

àExample: A dissecting microscope would be used to figure out the sex of the dragon flies. While a compound would be used if wanted to see the cells of its eye.

3)      What was the most obvious difference between animal cells and plant cells?

Animal cells don't have the cell wall, vacuole and chloroplast but plant cells have all of them.

4)      How and why does plasmolysis occur? What does this have to do with wilting?

   -Plasmolysis is when a cell shrinks due to water leaving. It happens when the

    pressure decreases to the point where the protoplasm of the cell peels away from

       the cell wall, leaving gaps between the cell wall and the membrane.

       When plant lost their water, the cells would also lose their turgidity; therefore the

       plants would wilt in this process.