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This lettuce project demonstrates cell diffusion, passive diffusion and selective barrier




9, 10, 11, 12  

Title – Lettuce Project
By – Vernon Alexander
Primary Subject – Science
Grade Level – 9-12


    How do materials move in and out of a cell?


    1 & 2 Scientific Thinking and Communication


  1. Students will use a lettuce leaf to discover the function of a cell membrane.
  2. Students will look at a multicellular lettuce and make-believe that it is a one-cell structure.
  3. Students will try to figure out what would be allowed into a cell by predictions, observations and by explanation.
  4. Students will do an experiment to show the movement of water into and out of the cell.
  5. Students will be able to state that the cell membrane lets materials in and out of a cell.

Do Now:

      #1 Predict what would happen if you placed a piece of lettuce into a salt solution?


      #2 Predict what would happen if you placed a piece of lettuce into food coloring?


    #3 Predict what would happen if you placed a piece of lettuce into a mixture of water and black pepper?


Salt Solution
Water & Food Coloring
Water & Black Pepper





      Data and Observations:

      Hypothesis #1:


      Hypothesis #2:


      Hypothesis #3:



      1. Explain what happened to the lettuce leaves after being placed into various beakers or cups.

      2. What can go into and out of a lettuce leaf?

      3. What happened when a lettuce leaf was placed in a beaker containing various spices, black pepper and/or nutmeg?

      4. Using a lettuce leaf to represent a cell membrane, can everything go into a cell?

      5. A leaf is a collection of many cells. What did you observe when you added food coloring?

Going Further:

      Will changing the amount of salt in the solution affect the amount of water in the lettuce leaf? Form a hypothesis to this question. Design an experiment to test your hypothesis.


      When working on the experiment, you used salt on the lettuce leaf. Explain how the preservation of food can be possible (salt-fish, pork, meat products). Also, use reference materials to investigate how we used diffusion and selective barrier in our experiment with the lettuce leaf.


Misconceptions: Activity: Scientific Principle:
Movement inside the cell membrane, but not out of the cell. #1 – Lettuce placed in a beaker with salt solution. Diffusion: Low to high concentration of salt
Nothing happens. #2 – Shriveled lettuce placed into a beaker of water. Passive Diffusion: High concentration of water to low concentration of water.
Everything goes in freely. #3 – Lettuce placed in a mixture of black pepper or nutmeg or fine spices without any salt. Selective barrier: It lets certain things into a cell, but not others.

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