1.0 ABSTRACT

Cells are the basic functional units of all living organisms. They may exist singly or in aggregates. When cells join together to take on a specialized function within a larger organism, they form a tissue. The cell is divided into two groups which are animal and plant cell. This experiment is conducted to investigate the structure of animal cell and plant cell by using onion and chicken as a specimen. Apart from that, it is carried out to understand how the microscope operates and study the differences between animal and plant cell. The microscope is used in the experiment to observe the specimen. In this experiment, the small section of onion and chicken is cut and put on the slide. A drop of safranine solution is added and the observation is recorded. The best image recorded when the 40X magnification is used. The structure of onion and chicken cell can be seen clearly. As the magnification increased, the more clear observation can be made.

1

2.0 INTRODUCTION

All living things are made up of tiny little units called cells. A cell is a basic unit of

all forms of life, but it is also the smallest living thing in the world. Cells consist of

an outside boundary called the cell membrane and inside the cell there is material

that known as cytoplasm. There are two classifications of cell which are plant and

animal cell.

2.1 Plant cell

An onion is a multicellular (consisting of many cells) plant organism. As in all plant

cells, the cell of an onion peel consists of a cell wall, cell membrane, cytoplasm,

nucleus and a large vacuole. The nucleus is present at the periphery of the cytoplasm.

The vacuole is prominent and present at the centre of the cell. It is surrounded by

cytoplasm. The presence of a cell wall and a large vacuole are indicators that help

identify plant cells, such as seen in the onion peel (Sullivan, 2015).

Figure 1: The structure of onion peel cells (Online Labs, n.d)

2.2 Animal cell

As in all animal cells, the cells do not possess a cell wall. A cell membrane that is

semi-permeable surrounds the cytoplasm. Unlike plant cells, the cytoplasm in an

animal cell is denser, granular and occupies a larger space. The vacuole in an animal

cell is smaller in size, or absent. The nucleus is present at the centre of the cytoplasm.

2

The absence of a cell wall and a prominent vacuole are indicators that help to

identify animal cells, such as cells seen in the chicken fat or human cheeks.

Figure 2: The structure of cheek cells (Online Labs, n.d)

2.3 Compound microscope

In order to observe the structure of cells and examine differentiation between animal

and plant cell, a microscope play the main role in the experiments. First, the purpose

of a microscope is to magnify a small object or to magnify the fine details of a larger

object in order to examine minute specimens that cannot be seen by the naked eye.

The compound microscope has its parts and plays their function together.

Figure 3: The part of compound microscope and its functions (Trimpe, 2003).

3

3.0 OBJECTIVE

To determine the structure of plant cells and animal cells.

To investigate how to handle the microscope and its function.

To understand the differences between plant cells and animal cells.

4.0 THEORY

The compound light microscope is a microscope with more than one lens and has its

own light source. These microscopes have an ocular lenses in the binocular eyepieces

and objective lenses in the rotating nosepiece closer to the specimen. All of the parts

of a microscope work together as the light from the illuminator pass through the

aperture, through the slide, and through the objective lens, where the image of the

specimen is magnified. Then, magnified image continues up through the body tube

of the microscope to the eyepiece, which further magnifies the image the viewer then

sees.

4.1 Magnification

Usually, the compound light microscopes have the lowest power lens is 3.5 or 4x and

is used primarily for finding the specimens. The most often used objective lens is the

10x lens as it gives a final magnification of 100x with a 10x ocular lens. For

example, when deal with a very small protest and for details in prepared slides such

as cell organelles or mitotic figures, the higher magnification is needed (Caprette,

2012).

In more details, in order to determine the total magnification, take the power of the

objective lens which is 10x or 40x and multiply it by the power of the ocular or

eyepiece which is normally 10x. Therefore, a 10x eyepiece used with a 40x objective

lens will produce a magnification of 400x. The naked eye can view the image or

specimen 400 times greater of magnified and microscopic details is discovered.

4

Table 1: The total magnified of an object by microscope (Amrita, n.d)

Magnification of ocular

lens

Magnification of objective

lens

Total magnification

10X 4X 40X

10X 10X 100X

10X 40X 400X

10X 100X 1000X

Normally, high magnification lenses are 40x and 97x or 100x. The last two

magnifications are used totally with oil in order to improve resolution. Each time the

power of objective lens is higher, the specimen should be re-focus and re-center as

the magnification lenses are closer to the specimen which poses the risk of jamming

the objective lenses into the specimen. Lower magnification is impossible on a

compound microscope stand because of spatial constraints with the image correction

and illumination. Meanwhile, higher magnification is impractical because of the

limitations in light gathering ability and shortness of working distance required for

very strong lenses (Wolniak, 2004). Parfocal are the good quality of lenses that is

when magnification is change, the specimen remains in focus or closed to focus. All

specimens have three dimensions and unless the specimen is extremely thin, the high

magnification objective will be unable to use. The higher the magnification, the

harder it is to "chase" a moving specimen.

Magnification is the ability to view an object as larger. A good image is obtained

when the amount of specimen detail is also increased. Magnification alone will not

achieve this.

4.2 Image Formation

The direct light from a specimen is projected by the objective and it spreads evenly

across the entire image plane at the diaphragm of the eyepiece. The light diffracted

by the specimen is come to focus at different localized sites on the same image plane,

and the diffracted light causes destructive interference. One of the consequences is

the reduction in light intensity resulting the greater or lesser dark areas. The patterns

of light and dark that are recognized as an image of the specimen as the eyes are very

5

sensitive to variations in brightness, and then the image becomes more or less

faithful reconstitution of the original specimen (Amrita, n.d). The objective lens at

first formed a real and inverted magnified image. Then the eye piece further

magnifies the same image to virtual magnified image.

5.0 MATERIAL AND APPARATUS

Material: Onion (plant cell), chicken fat (animal cell), safranin solution and distilled

water.

Apparatus: Compound microscope, microscope slides, cover slips, forceps, knife.

6.0 PROCEDURE

Plant cell

1. A small section of onion skin was peel off.

2. The onion skin was placed in the centre of the slide.

3. Two drops of water were placed on the onion skin and this situation known as

“wet mount”.

4. Then, a cover slip was lower over the onion skin gently.

5. The slide was tap with a pen to remove any air bubbles.

6. A drop of safranin solution was dropped at one edge of the cover slip.

7. The slide was placed on the stage under low power. The coarse adjustment

knob was used to focus on the sample.

8. Then, the nosepiece was rotate to medium power (4X). The knob adjustment

was used to focus and the observation was recorded.

9. The step 8 was repeated by changing the focus to high power (10X and 40X).

Animal cell

1. A small section of chicken skin was cut using the knife.

2. By using forceps, the chicken skin was placed in the centre of the slide.

3. The wet mount was prepared like in step 3-9 by using the same solution

which was safranin solution.

4. All the observation was drew in the paper.

6

7.0 RESULT

Magnification

Cells

Onion cell Chicken cell

4X

10X

40X

8.0 DISCUSSION

Based on the result, the plant cell and animal cell showed the different structure

towards each other. The onion cell structure is a rectangular in shape. It had a cell

wall and nucleus when observe with the microscope. Meanwhile, the structure of

chicken cell is circle in shape. It has the cell membrane which is the outer most

layers in the animal cell that separates the contents of the cell from the outside world.

It consists of both lipids and proteins and is selectively permeable, which means it

permits only some molecules to pass through it (Cooper, 2000).

Compound microscope was used to observe the cell. The objective lenses used were

4X, 10X and 40X. When the microscope’s total magnification was 40X, there were

7

about a hundred rows of rectangular cells but as the magnifications changed, the

number of cells in the field of view decreased. When the onion skin cells viewed at

400X total magnification, the nuclei of the cells looked clearer and larger compared

to the first magnification. The organelles such as the cytoplasm and the cell wall had

been seen. Unlike the onion skin cells, the chicken cells were more spread out from

each other and they all had a round shape. When the chicken cells were viewed at

40X total magnification, the cells were secluded and spread out. At 400X total

magnification, only one cell was viewed at a time, due to the fact that the cells were

separated from each other. The organelles those were visible in this type of cell were

the nucleus, the cytoplasm and the cell membrane. Aside from the actual cells, the air

bubbles had been seen within both the onion skin cell slide and the chicken cell slide.

This happen because the air bubbles were trapped within the slide. The air bubbles

should be removed by tapping the slide with pen or pencil during the experiment.

The animal cell is a little bit different than the plant cell for only a couple of reasons.

One is how the plant cell has a cell wall and the animal cell does not have it. The cell

wall protects and gives structure to the cell. The presence of a cell wall is what

provides the most significant difference between plant and animal cells, as it is

present only in plant cells and covers the cell membrane. The cell wall is rigid and is

composed of cellulose fibre, polysaccharides, and proteins. Despite the rigidity of the

cell wall, chemical signals and cellular excretions are allowed to pass between cells.

Apart from that, the plant cell have the cytoplasm meanwhile the animal does not

have it. Cytoplasm is a jelly-like material that is eighty percent water and is usually

clear in colour. It is also called cytosol. Cytoplasm contains all the organelles inside

the cell membrane. The cytosol contains dissolved nutrients, helps break down waste

products, and moves material around the cell through a process called cytoplasmic

streaming (Online Labs, n.d).

9.0 CONCLUSION

In this experiment, the structure of animal and plant cell can be identified via the

microscope. The microscope plays the main role in identification of cell. The

microscopes have objective lenses and ocular lenses where a magnified image of the

specimen is produced by the objective lens and image is magnified by ocular lens for

viewing. The specimen will be clearer as the total magnification increased. Through

8

this experiment, the different between animal and plant cell have been identified. The

plant cell has the cell wall, cytoplasm and vacuole. Unlike the plant cell, the animal

cell has cell membrane that controls the movement of substance in and out of the

cell.

10.0 RECOMMENDATION

There are a few of recommendation should be practice to improve the result of the

experiment such as:-

Make sure the cell used is thin to get the accurate result.

Make sure to remove air bubbles by tapping the slide with a pen or pencil.

Handling the microscope properly. Once the cell is found, use the adjustment

knob to change the power focus but do not use the coarse adjustment knob.

Make sure the objective lens and ocular lens is clean using paper lens when

the images of specimens are blurred at particular power.

11.0 REFERENCES

Amrita V. V. (n.d.). Light Microscope (Theory): Cell biology Virtual Lab I: Biotechnology and

Biomedical Engineering: Virtual Lab. Retrieved from http://amrita.vlab.co.in/?

sub=3&brch=187&sim=323&cnt=1

Caprette, D. R. (2012, August 10). Light microscopy. Retrieved from

http://www.ruf.rice.edu/~bioslabs/methods/microscopy/microscopy.html

Cooper, G.M. (2000). The Cell: A Molecular Approach. 2nd edition. Sunderland

(MA): Sinauer Associates; 2000. Structure of the Plasma

Membrane. Available from: http://www.ncbi.nlm.nih.gov/books/NBK9898/

Online Labs (n.d). Onion and Cheek Cells (Theory) : Class 9 : Biology : Amrita Online Lab.

Retrieved from http://amrita.olabs.co.in/?sub=79&brch=15&sim=125&cnt=1

Sullivan, J. A. (2015). Interactive Eukaryotic Cell Model. Retrieved from

http://www.cellsalive.com/cells/cell_model.htm

Wolniak, S. M. (2004). Principles of Light Microscopy. Retrieved from

http://www.life.umd.edu/cbmg/faculty/wolniak/wolniakmicro.html

Trimpe, T. (2003). Parts of the Light Microscope. Retrieved from

http://sciencespot.net/Media/microparts.pdf

9

12.0 APPENDIX

Onion Cell Chicken Cell

4X: 4X:

10X: 10X:

40X: 40X:

10