1.0 ABSTRACT

Plant cells and animal cells are eukaryotic cells as both have a nucleus. All plant cell consists

of a cell wall, cell membrane, cytoplasm, nucleus and large vacuole. Animal cells are similar

to plant cells. However, they lack cell wall and large vacuole. In this experiment 1, we are

using optical microscope to observe onion skin cells and human cheek cells. We want to

examine, to know the characteristic and to differentiate human cheek cells and onion skin

cells. In this experiment, a small bit of an onion was cut off. The outermost and the thinnest

layer of the onion was peeled. This layer is the onion skin cells. To obtain the cheek cells, the

inside lining of the cheek was gently scraped with a sterile cotton swabs. Both onion skin

cells and human cheek cells are placed on the glass slide. Then, the glass slide was dropped

with a few drops of safranin. The slides were observe under optical microscope with

magnification of 100x, 400x, and 1000x. During observation, the onion skin cells have a

fixed shape due to the presence of the cell wall. While animal cells have irregular shape due

to absent of any cell wall. With the presence of cell wall, onion skin cells is classified as plant

cells. Since human cheek cells lack any cell wall, they are classified as animal cells.

2.0 INTRODUCTION

Anton van Leeuwenhoek is regarded as the father of Microbiology. His vast contribution in

Microbiology allows him to receive that title. In 1673, Leeuwenhoek discovered the existence

of microorganism. He used a simple microscope consist of a single biconcave lens to aid in

his discovery. This discovery sparks a new beginning of Microbiology. Microscope has

undergoes drastic changes throughout the time. Starting with the simple microscope created

by Leeuwenhoek with magnification of 300x, to the powerful electron microscope with

magnification of more than 250000x. This shows how important microscope in

Microbiology.

In this experiment, optical microscope was used to observe the onion skin cells and human

cheek cells. Onion and cheek cells were observed under optical microscope at a

magnification of 100x, 400x and 1000x. We also want to observe the cell shape and several

organelles of the cells. When observed under the optical microscope, the cell shape and

organelles of onion and cheek cell should be slightly different. These characteristics may

classify them either as plant cell or animal cell.

To obtain the onion skin cell, a small bit of the onion was cut off. Onion skin was ripped

carefully from the onion bit until the smooth and thin white layer was peeled off. Then, the

white layer was carefully spread out on the glass slide. A few drops of distilled water were

dropped on the slide. Then, a few drops of safranin were dropped on the slide. Cover slip is

carefully placed on the glass slide to avoid formation of air bubbles. A piece of tissue is used

to remove excess solution on the glass slide. Then, the slide was placed on the stage of the

microscope to prepare for observation. The observation is started with magnification of 100x.

Then, the magnification is changed to 400x and 1000x. The focus knob was adjusted to

obtain the clearest image possible. The structures, organelles and shape of the cell were

observed.

Meanwhile, the human cheek cell were obtained by scrapping the inside of the cheek with

sterile cotton swab. It should be scrapped gently so to avoid hurting the cheek. Then, a few

drops of distilled water were dropped on the glass slide. The sterile cotton swab was gently

rolled on the glass slide. Then, a few drops of safranin were dropped on the slide to stain the

cheek cell. Cover slip is carefully placed on the glass slide to avoid formation of air bubbles.

A piece of tissue is used to remove excess solution on the glass slide. Then, the slide was

placed on the stage of the microscope to prepare for observation. The observation is started

with magnification of 100x. Then, the magnification is changed to 400x and 1000x. The

focus knob was adjusted to obtain the clearest image possible. The structures, organelles and

shape of the cell were observed.

3.0 OBJECTIVES

1. To examine human cheek cells and onion skin cells.

2. To know the characteristic of plant cells and animal cells.

3. To differentiate between plant cells and animal cells.

4.0 THEORY

Onion Cell

An onion is a multicellular plant organism. The onion epidermis contain plant cells which is

present in all plants. All plant cells consist of a cell wall, cell membrane, cytoplasm, nucleus

and vacuole. A cell membrane is semi-permeable and surrounds the cytoplasm. The nucleus

controls the metabolic rate of the cell, is located near the vacuole in the cytoplasm. The

vacuole has the largest size in the cytoplasm and usually located at the centre of the cell. Both

nucleus and vacuole is surrounded by cytoplasm. The presence of a cell wall and a large

vacuole are key points that help recognise plant cells, such as in the onion epidermis.

Plant cells are similar to animal cells in that they are both eukaryotic cells and have similar

organelles. Plant cells are generally larger than animal cells. While animal cells come in

various sizes and tend to have irregular shapes, plant cells are more similar in size and are

typically rectangular or cube shaped. A plant cell also contains structures not found in an

animal cell. Some of these include a cell wall, a large vacuole, and plastids. Plastids, such as

chloroplasts, assist in storing and harvesting needed substances for the plant.

Human Cheek Cell

The human cheek cell is an animal cell. All animal cells consist of a cell membrane,

cytoplasm, and nucleus. A cell membrane is semi-permeable and surrounds the cytoplasm. At

the centre of the cytoplasm the nucleus is usually located. Unlike plant cell, animal cell does

not have a cell wall, it only have a cell membrane. Compare to the plant cell, the vacuole in

an animal cell is smaller in size and sometimes it may be absent. The absence of cell wall are

indicators that helps to differentiate between animal cells and plant cells, such as cells seen in

the human cheek.

Animal cells are similar to plant cells in that they are both eukaryotic cells and have similar

organelles except chloroplast. Animal cells are generally smaller than plant cells. Animal

cells come in various sizes and tend to have irregular shapes, while plant cells are more

similar in size and are typically rectangular or cube shaped. Animal cells also contain

structures such as centrioles, lysosomes, and cilia and flagella that are not typically found in

plant cells.

Cell Wall

The presence of a cell wall is the most important key to differentiate between plant and

animal cells. This is because it is only present in plant cells. Animal cell lack cell wall. The

cell wall enclosed the cell membrane of the plant cell. It is rigid and is composed of cellulose

fibre, polysaccharides, and proteins. This rigidity also helps plant cell to obtain a fixed shape,

usually rectangular shape. Despite the rigidity of the cell wall, chemical signals and cellular

excretions are allowed to pass between cells.

Cell Membrane

The cell membrane is found in both plants and animals cell. It is the outer most layer in the

cell that separates the cytoplasm of the cell from the outside substances. It consists of both

lipids and proteins and is selectively permeable. This means it permits only some molecules

to pass through it.

Cytoplasm

Cytoplasm is a jelly-like material that is eighty percent water and is usually colourless. It is

also called cytosol. Cytoplasm contains all the organelles and it is enclosed by cell

membrane. It also contains dissolved nutrients and helps break down waste products by using

enzymes.

Nucleus

The nucleus and acts as the control centre of the cell. It is responsible to regulate all the

activities inside the cell. Usually, it is the largest organelle in the cell. However, for most

plant cell, nucleus is the second largest organelle after vacuole. The nucleus also contains the

DNA of the cell. DNA contains all the information that helps cells live, perform their

functions and reproduce. The nucleus has a double layered membrane called nuclear

membrane.

Vacuoles

A vacuole is a membrane-bound organelle that contains solid or liquid contents. Vacuoles are

found in both animal and plant cells, but are much larger in plant cells. In fact, for most plant

cell, it is the largest organelle. In animal cell, vacuole is small and sometimes it may be

absent. Vacuoles are formed by the fusion of multiple membrane vesicles and are effectively

just larger forms of these. The organelle has no basic shape or size; its structure varies

according to the needs of the cell.

5.0 PROCEDURES

PLANT CELL

1. A small bit of an onion was cut off. The outermost and the thinnest layer of the onion was

peeled. This layer should be thin enough to be translucent.

2. The specimen, which is the thin onion skin was placed on the glass slide and a few drops

of distilled water were dropped.

3. A few drops of safranin were dropped on the glass slide and the glass slide was covered by

cover slip carefully to ensure no air bubbles were formed.

4. The glass slide was placed on the stage of microscope and clipped to stay in place.

5. The observation of the specimen was started with magnification of 100x, 400x and 1000x.

6. The focus knob was adjusted to obtain clearer image.

7. The specimen was observed and drew.

ANIMAL CELL

1. The inside lining of the cheek was gently scraped with a sterile cotton swabs.

2. A few drops of distilled water were dropped on the glass slide and the sterile cotton swabs

was gently tapped on the glass slide.

3. A few drops of safranin were dropped on the glass slide and it was covered carefully with

cover slip to prevent air bubbles.

4. The glass slide was placed on the stage of microscope and clipped to stay in place.

5. The observation of the specimen was started with magnification of 100x, 400x and 1000x.

6. The focus knob was adjusted to obtain clearer image.

7. The specimen was observed and drew.

6.0 APPARATUS

Apparatus Function

Optical microscope To observe the specimen with various

magnification.

Onion skin The specimen which contain plant cells

that will be used to be observed under

the microscope.

Cheek cell The specimen that will be used to be

observed under the microscope.

Glass slide Small slide which allow specimen to be

placed. It is placed on the stage of the

microscope.

Cover slip A thin and transparent plastic slip to

cover the specimen on the glass slide

Safranin Used to stain the cells to be observed

better under the microscope.

Distilled water To wet the specimen on the glass slide

Razor knife Sharp knife to cut the onion.

Sterile cotton swabs Swabbed inside the cheeks to obtain cheek

cells

7.0 RESULTS AND CALCULATIONS

Plant cells

Magnification: 100x

Magnification: 400x

Plant cells

Animal cells

Magnification: 1000x

Magnification: 100x

Animal cells

Magnification: 400x

Magnification: 1000x

8.0 DISCUSSION

In this experiment, only nucleus, cytoplasm, cell wall, and vacuole were visible under optical

microscope. This however, is enough to know the characteristic of plant and animal cells.

Smaller organelles such as mitochondria can only be seen under electron microscope.

Next, I have found that the cheek cells have irregular shape. This is due to the lack of cell

wall that can maintain a fixed shape. Since animal cells lack of cell wall, this means that

cheek cells are animal cells, not plant cells. Inside the cytoplasm, there is a nucleus at the

centre of the cheek cells. The cheek cells are scattered randomly on the slide surface. Also,

the size varies slightly between each cells. Next, the cheek cells are also lack of visible

vacuole. Hence, I have determined that cheek cells are animal cells.

For the onion skin cells, I have found that it have a fixed shape and it closely resembles a

rectangle. The shape occurs due to the presence of the cell wall. This characteristic prove that

onion cheek cells are plant cells due to the presence of cell wall. Unlike animal cells, the

onion skin cells are positioned next to each other. Perhaps the fixed shape allows them to

form such arrangement. Inside the cytoplasm, there is a nucleus at the centre of onion skin

cell. Hence, I have determined that onion skin cells are plant cells.

In this experiment, I have found some differences between human cheek cells and onion skin

cells. Onion skin cells have cell wall while the cheek cell doesn’t have. Next, onion skin cells

have a fixed shape, while the cheek cells have an irregular shape. Also, the arrangement for

onion skin cells are next to each other. While for human cheek cells, they are randomly

placed.

Besides that, I have also found similarities for both onion skin cells and human cheek cells.

Both are eukaryotic cells as shown by the presence of nucleus. Both have cytoplasm and cell

membrane.

9.0 CONCLUSIONS

Onion cheek cells are plant cells since they have a cell wall. While human cheek cells are

animal cells because they lack cell wall. Plant cells have a fixed shape due to the presence of

cell wall while animal cells have irregular shape. Plant cells are arranged closely next to each

other. While animal cells are randomly scattered. Both plant and animal cell are eukaryotic

cells as shown by the presence of nucleus. Besides that, both of them have cell membrane,

and cytoplasm. Only plant cell have the cell wall.

10.0 RECOMMENDATIONS

At the end of this experiment, I have found that the results are similar with the theory. For

plant cells, I managed to observe cell wall, cell membrane, cytoplasm and vacuole clearly

under optical microscope. For animal cells, I managed to observe cell membrane, and

cytoplasm clearly under optical microscope. When preparing the slides, I have noticed that

there are presence of some air bubbles. To avoid unwanted air bubbles, one end of the cover

slip should be placed on the slide. Then, slowly lower the other end using the end of a

toothpick. This will help to prevent air bubbles from getting trapped under the cover slip.

11.0 REFERENCES

12.0 APPENDICES

Figure 1: Animal cell