Lesson 1.3 The light microscope

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Introduction to the lesson

Now that we have the basic understanding that all living things are composed of cells, we begin to move further and in this lesson we will learn how people study cells. Since cells are too small to be seen with the naked eye, every biology student must know about microscopy. In this lesson we will look at the light microscope -- how it works and what parts of the cell can be seen through it. Though we cannot see everything through the light microscope, some important organelles are visible and we can begin to see some structural differences between animal cells and plant cells. For many years, until the electron microscope was invented, this was the limit of how much we could know about the cell. Our view of the cell and our understanding of the organelles will expand much more when we study the cell through the electron microscope (Lesson 1.5-1.7).

Cell biology and microscopy

Read the section "Cell biology and microscopy" on p.3 in your text book.

Parts of the light microscope

Learning Activity 1

Answer the following questions in your exercise book.

  1. Study Fig. 1.3 on page 3. This shows the parts of a light microscope. Draw your own light microscope and label the parts.
  2. Use the diagram to show how the microscope works (i.e. add notes to the diagram).

Animal cells under a light microscope

Learning Activity 2

Answer the following questions in your exercise book.

  1. Study Fig. 1.4 on p.3. This shows a generalized animal cell under a light microscope. Compare Fig. 1.4 with Fig. 1.6 (p.4) which is photomicrograph of actual animal cells. Using the labels of Fig. 1.4 can you distinguish features of the cells in Fig. 1.6?
  2. Draw and label the structure of a generalized animal cell (i.e. copy Fig. 1.4). (Refer to Box 7.1 on p. 129 of your text book for precise instructions on how to make a biological drawing.)
  3. Draw a biological drawing of the cells in Fig. 1.6.

Plant cells under a light microscope

Learning Activity 3

Answer the following questions in your exercise book.

  1. Study Fig. 1.5 (p.4) which is a diagram of a generalized plant cell. Compare Fig. 1.5 with Fig. 1.7 (photomicrograph of plant cells; p.4). Using the labels of Fig. 1.5 can you distinguish the features of the cells in Fig. 1.7?
  2. Draw and label the structure of a generalized plant cell (i.e. copy Fig. 1.5).
  3. Draw a biological drawing of the cells in Fig. 1.7.

Comparing animal and plant cells under a light microscope

Learning Activity 4

Compare Fig. 1.4 and 1.5. Answer the following questions in your exercise book.

  1. List all the features both cells have in common.
  2. List all the features that are unique to:
    1. Animal cells
    2. Plant cells

Read the section "Animal and plant cells have features in common" and "Differences between animal and plant cell" on p.5-6 of your text book and answer the following questions in your exercise book.

  1. Compare your own lists above with the text under the headings: “Animal and plant cells have features in common” and “Differences between animal and plant cells”.
  2. Add to your lists any feature which you might not have mentioned.
  3. Answer Question 1.1 on p.4.

Definitions and review

Definitions

  1. Cell biology
  2. Cytology
  3. Cell surface membrane
  4. Nucleus
  5. Chromatin
  6. DNA
  7. Nucleolus
  8. Cytoplasm
  9. Organelles
  10. Mitochondria (sing. mitochondrion)
  11. Golgi apparatus
  12. Centriole
  13. Cell wall
  14. Plasmodesmata (sing. plasmodesma)
  15. Vacuole
  16. Tonoplast
  17. Chloroplasts
  18. Cholorophyll
  19. Grana (sing. granum)
  20. Thylakoids

Mindmap

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