Page 9 - Focus PT3 2020 Science ( BI Version )

Science PT3 Chapter 2 Cell as the Basic Unit of Life

Eksperimen 2.1
Activity 2.2
Eksperimen 2.1
Aim: To prepare a plant cell slide and to examine plant cells (epidermal
cells of an onion bulb) Onion
scale
Materials and apparatus: Onion bulb, iodine solution, distilled water,
Form
Form
1 filter papers, glass slide, cover slip, light microscope, dropper, mounting Epidermal layer of onion
needle, scalpel and forceps.
Procedure:
1. A drop of distilled water is placed on the centre of a clean slide.
2. An onion scale is cut using a scalpel and an epidermal layer from it
is peeled off using a forceps.
3. The epidermal layer is then placed in the middle of the water drop on
the slide.
Epidermal layer
4. A cover slip is lowered slowly on the specimen using a mounting needle of onion
to ensure that air bubbles are not trapped under the cover slip.
5. A drop of iodine solution is placed on one edge of the cover slip and
a filter paper is held at the other edge of the cover slip to draw the Mounting
needle
iodine solution across the slide to stain the cells.
6. Excess iodine solution is absorbed using another piece of filter paper. Cover slip
7. The slide is observed under the low power objective lens of the light
microscope, followed by the high power objective lens.
8. The structure of the epidermal cells is drawn and labelled
accordingly.

Observations: Figure 2.7 Preparing the
slide of epidermal cells
Membrane cell
Cell wall Tips

Nucleus Methylene blue solution is
Cytoplasm usually used to stain animal
Vacuole cells, while iodine solution is
used to stain plant cells.
Figure 2.8 Epidermal cells of an onion bulb
Discussion: TIMSS Challenge 2
1. Iodine solution stains the nucleus brown so that the structure of
epidermal cells can be seen clearly. Name two structures that are
2. Epidermal cells of onion bulb have a fixed shape. found in plant cells but not in - 21
animal cells.
AK
PAK-21
P
3. The structures of the epidermal cells as seen under the light
microscope are the cell wall, cell membrane, nucleus, cytoplasm
and vacuole.
4. Onion cells do not contain chloroplasts.
Conclusion:
A plant cell has a fixed shape, a nucleus, cell membrane, cytoplasm, cell wall and vacuole.

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