Grade 8 Integrated Science Notes: The Cell (Plant and Animal Cells, Microscope, Magnification)

Grade 8 Integrated Science · Strand 2.0 Living Things and Their Environment · Sub-strand 2.1 The Cell

These are free study notes for Grade 8 learners, written to the KICD curriculum design and taken from our full Grade 8 Integrated Science notes. Expect to label a plant or animal cell, compare the two in a table, and calculate magnification. All three are covered below.

Every living thing is made of cells, the smallest units that can carry out life processes. Most are too small to see without a microscope. In this topic we use the light microscope, prepare and observe plant and animal cells, describe their parts and functions, compare them and calculate magnification.

Cells and the light microscope

Using a microscope

1. Carry it with one hand on the arm and the other under the base.
2. Start with the low-power objective; adjust the mirror for bright light; clip the slide.
3. Looking from the side, lower the objective close to the slide with the coarse knob.
4. Look through the eyepiece and raise it slowly until the image is clear; use the fine knob at high power.

Plant cells

For onion cells: lay the thin inner skin of an onion scale leaf in a drop of water, lower a cover slip at an angle to avoid air bubbles, and draw iodine under it to stain the parts. The cells look like rows of bricks. Onion cells have no chloroplasts because the scale leaf grows underground; a moss leaf shows many green chloroplasts without staining.

Animal cells and comparison

Animal cells (such as cheek cells) are irregular or round, with a cell membrane, cytoplasm and a nucleus but no cell wall, so they can change shape. Vacuoles are small and temporary, if present.

Magnification

At higher magnification fewer cells are seen, but each is larger and more detailed; the image is darker, so open the diaphragm a little.

Drawing, organisation and specialised cells

• Biological drawing: sharp pencil; single continuous lines; no shading; at least half a page; ruled label lines that do not cross; a title and the magnification.
• Specialised cells: root hair cells (absorb water), red blood cells (carry oxygen; no nucleus when mature), nerve cells (carry messages), guard cells (open and close leaf pores).
• Safety: plant waste to the compost pit; broken glass picked up with a brush and pan into a labelled container; wash and dry slides.

Test yourself: multiple choice

1. Which part is found in plant cells but NOT in animal cells?

   1. Nucleus
   2. Cell wall
   3. Cytoplasm
   4. Cell membrane
   Show the answer

   B: Animal cells have no wall.

2. Eyepiece ×10 and objective ×40 give a total magnification of

   1. ×400
   2. ×50
   3. ×4
   4. ×30
   Show the answer

   A: 10 × 40 = 400.

3. Which part controls the activities of the cell?

   1. Vacuole
   2. Cell wall
   3. Chloroplast
   4. Nucleus
   Show the answer

   D: The nucleus controls the cell.

4. Why are there no chloroplasts in onion scale cells?

   1. They were stained away
   2. Onions are animals
   3. The scale grows underground away from light
   4. They are too small
   Show the answer

   C: No light, no chloroplasts.

5. Which knob is used for sharp focusing at high power?

   1. Mirror
   2. Coarse adjustment knob
   3. Diaphragm
   4. Fine adjustment knob
   Show the answer

   D: Fine adjustment.

Practice questions

1. State the function of: cell wall, vacuole, chloroplast, cell membrane. (4 marks)

   Show the answer

   Wall: shape and support; vacuole: stores sap, keeps cell firm; chloroplast: photosynthesis; membrane: controls entry and exit.

2. Give two similarities and three differences between plant and animal cells. (5 marks)

   Show the answer

   • Similar: membrane, cytoplasm, nucleus (any two)
   • Different: plant cells have a wall, a large vacuole and chloroplasts; animal cells do not

3. Calculate the total magnification: (a) eyepiece ×5, objective ×40 (b) eyepiece ×10, objective ×10. (2 marks)

   Show the answer

   (a) 5 × 40 = ×200 (b) 10 × 10 = ×100.

4. Describe how to prepare a temporary slide of onion cells. (4 marks)

   Show the answer

   Put a drop of water on a slide; lay the thin onion skin flat in it; lower a cover slip at an angle; stain with iodine drawn under the cover slip.