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Activity: Identifying Cells and Cell Parts Using a Microscope

NGSS Science and Engineering Practices:

NGSS Crosscutting Concepts:

NGSS Disciplinary Core Ideas:

Materials

  • Table 2.2
  • Compound light microscope
  • Elodea species or other freshwater aquarium plant
  • Two microscope slides
  • Cover slips
  • Pipette
  • Fresh water
  • Saltwater

Procedures

A. Observe Elodea sp. cell parts.

  1. Define cell membrane, cell wall, and chloroplast.
     
  2. Remove an Elodea leaf and place it in the middle of a microscope slide.
     
  3. Using a pipette, drop fresh water on top of the Elodea to cover the leaf.
     
  4. Place a cover slip on top of the Elodea.
     
  5. Place the Elodea slide under a compound microscope at the lowest setting. Observe Elodea through the microscope.
     
  6. Draw what you see in one of the circles in Table 2.2. Label the circle with the appropriate magnification. Label the structures that you can see (e.g., cell wall, membrane, or chloroplasts).
     
  7. Repeat step 7 for higher settings of the microscope. Note: Be sure to only use the fine focus at the highest setting of the microscope so that you don’t damage the microscope lens.
     
  8. Optional: Chloroplasts look like green ovals within the cell. At an appropriate objective setting, choose three to ten Elodea cells. Count the number of visible chloroplasts per cell. Calculate the average and compare with the class.

 

B. Adding salt solution to the Elodea slide.

  1. Remove an Elodea leaf and place it in the middle of a second microscope slide.
     
  2. Using a pipette, place drops of salt water on top of the Elodea to cover the leaf.
     
  3. Place a cover slip on top of the Elodea.
     
  4. Repeat Part A, steps 7 and 8.

 

Activity Questions: 
  1. Cell membranes
    1. Describe the components of a cell membrane.
    2. How are cell membranes important to living organisms?
       
  2. Was it difficult to distinguish the cell membrane and cell wall in Part A? Part B? Explain.
     
  3. Chloroplasts
    1. Did the number of chloroplasts vary between cells on your slide?
    2. Did the number of chloroplasts per cell vary in your class? Explain.
       
  4. Adding salt to the outside of a plant can cause water molecules to flow from inside the plant to outside of it. Explain the effect of adding salt solution to Elodea. Describe how these structures changed (or did not change).
    1. cell wall
    2. cell membrane
    3. chloroplasts
       
  5. Consider the structure and function of the cell wall and the cell membrane.
    1. Which structure is primarily responsible for the stability of a plant?
    2. Which structure is responsible for allowing substances to enter and exit the cell?
    3. What evidence did you observe to support your answers?
       
  6. Based on your observations, how can you tell that Elodea is a eukaryotic organism?
Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.