PRACTICAL 3: OBSERVATION OF ANIMAL CELL: CHEEK CELL AND PLANT CELL: LEAF EPIDERMAL CELL

Objective: To prepare slides of animal cell and plant cell using the correct staining technique.

Introduction: All living things are made up of basic units called cells.

Hypothesis: Inner cheek cells have a nucleus, plasma membrane and cytoplasm where as leaf epidermal cells have a nucleus, plasma membrane, cytoplasm, cell wall and chloroplast.

Inferences: All cells share certain general characteristics.

Variables:

a) Manipulated: Types of cells usedb) Responding: The structure and component of the cellsc) Constant: The reagent that we used to stain the cells

Literature review:

Animal cells and plant cells have similarities and differences. An animal cell does not have a fixed shape and cell wall where as a plant cell have a fixed shape and surrounded by a cell wall. Like a plant cell, an animal cell has a plasma membrane, cytoplasm and nucleus. Plant cells that carry out photosynthesis process have chloroplast. This info is extracted from Biology Success Book SPM by Gan Wan Yeat.

Materials and apparatus:

Microscope, microscope slide, cover slip, dropper, forceps, blade, toothpick

Methylene blue, iodine solution, check cell and onion

Procedure:

a) Observation of check cells

1. The mouth is rinsed2. By using a toothpick, a thin layer of cell are scraped off from the inside

of your check. 3. The scrapings are mouthed in a drop of methylene blue solution on a

slide.4. The cover slip is gently lowered over it.5. The specimen is examined under low power objective lens followed by

high power objective lens.

6. The check cell is drawn and the following parts: nucleus, chromatin material, cell membrane and cytoplasm is labelled.

If you do not like to use your own check cells, you can look at dead skin cells instead. Put a small piece of sellotape on your hand and then peel it off and stick it down to a slide. This will show you the size and shape of cells but you will not be able to see the contents.

b) Observation of leaf epidermal cells

1. By using a forceps, the epidermal layer of onion scale leaf is peeled off.2. A small piece is cut off and the epidermal layer is mounted in a drop of

iodine solution on a slide.3. The cover slip is gently lowered over it.4. The specimen is examined under low power objective lens followed by

high power objective lens.5. The onion leaf epidermal cell is drawn and the following parts: nucleus,

chromatin material, cell membrane, cell wall, cytoplasm and vacuole is labelled.

To see plant cells with chloroplasts you could look at moss leaves in the same way. They are only one cell thick.

Results:

Drawings and labelling

Magnification of drawing

Discussion:

Questions:

1. Name the type of cells which lines the inner cheek

Epithelium cell

2. Why it is that onion leaf epidermal cell do not contain chloroplast?

The onion leaf epidermal cell does not contain chloroplast because it does not carry out photosynthesis process.

3. State the similarities and differences between animal cells and plant cells.

Types of cell Similarities Differences

Animal cells Both cells have plasma membrane, a nucleus,

and cytoplasm

Do not have cell wall, chloroplast and does not have fixed shape

Plant cellsHave a cell wall,

chloroplast and have a fixed shape

4. Why the nucleus is called the ‘control centre’ of the cell?

It is because it can produce enzyme which is control all the activities of the cell.

5. What is tissue? What word means collection of tissues doing one particular job?

Tissue is a group of cells which have become differentiated and specialised to carry out particular tasks. Collection of tissues doing one particular job is called an organ.

6. Try to find out: when cells were discovered and by whom?

In 1665, Robert Hooke, the English Scientist used a microscope to examine a thin slide of cork and described it as consisting of ‘a great many little boxes’ named ‘cells’ .

In 1838, German Botanist Mathhias Schleden found the first plant cells to be discovered. In 1839, also a German Zoologist Theoder Schwom found the first animal cell.

In 1855, a German Physician Rudolf Virchow induced that cells only come from other cells.

References:

Ching, L. (2005) Text Pre-U Biology Volume 1 (pp.194-204) Selangor : Pearson

Malaysia Sdn. Bhd.

Year,G.W. (2007) Success Biology SPM (pp.210-215) Selangor : Oxford Fajar

Sdn. Bhd.

L.S. Ching, L.S. Leong, Nalini B., Jacquelina R.S. (2005) Biology Matriculation

Semester 1 Second Edition (p.p 170-172) Selangor : Oxford Fajar Sdn. Bhd.

Dicking, W. R. (2000). Complete Biology. Spain: Oxford University Press.

Martin, J. (1999). Core Biology. United Kingdom: Cambridge University Press.

Martin, S. B. (2002). Biology. United Stated: Thomson Learning Publication.

(n.d.). Retrieved January 25 , 2010, from http://en.wikipedia.org/wiki/cells