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Lesson: Chapter 6 — The Structure and Function of Plant and Animal Cells

6.3. The structure of cells 2 of 5

Activity 02 — onion peel cells

Now a plant cell. The specimen is in the kitchen: separate a fleshy piece from an onion and the onion peel on it is thin enough to go straight under the microscope.

Materials

An onion, a watch glass of water, a brush, a glass slide, a cover slip, a light microscope.

Method

  1. Cut an onion and take a fleshy piece from inside it, as shown in figure 6.3 (a).
  2. Remove a peel from its inner or outer surface and drop it into a watch glass of water.
  3. Take a glass slide, put a drop of water on it, and use a brush to place the onion peel on that drop.
  4. Lower the cover slip carefully so that no air bubbles get in, and observe under the microscope.

Figure to be added

Figure 6.3 (a) — the four steps: cutting the onion, taking the fleshy piece, removing the peel, and mounting it on the glass slide.

Figure to be added

Figure 6.3 (b) — stained onion peel cells as they appear under the light microscope.

Observation

The cells fit together regularly, side by side, like brickwork. Each is enclosed by a straight, rigid boundary, and the nucleus is not in the middle but pushed against one side.

This is where the two activities part company

The onion peel cells have the rigid boundary the cheek cells did not, and their nuclei are pushed to one side because something the cheek cells did not have is occupying the middle. The next two pages do nothing but give those differences their names.