Materials: - Ziploc bag (any size)
- Sharpened pencil
- Playdoh or other material to make cell organelles
- Food Colouring
- Access to a sink with warm water
Procedure: 1. Fill a plastic bag just under ¾ full of warm water (too much water will spill out).
2. Add food colouring and Playdoh organelles then close the bag
3. Using a twisting motion, push a sharp pencil into the bag straight through to the other side
4. The bag will seal around the pencil, not allowing any of the water to leak out
Explanation:This lesson hook demonstrates cell permeability. It shows that material can move in and out of the cell without damaging the cell membrane. It also demonstrates that energy is expended in order to transport the material through the membrane. The plasma membrane is selective about what passes through it. So therefore, it allows desirable nutrients into the cell and keeps out undesirable nutrients. The nutrients then exit through the exterior of the cell. In this case the movement is driven by force. In order to increase the explanation to higher grade levels one could discuss the concept of diffusion and the demonstration of pressure differences driving movement.
Why this hook is a worthwhile activity: This hook is worthwhile to create a visual understanding of cell permeability and demonstrates for students the “choice” the cell has. This demonstration can be extended to using a pen to show that the pen will in fact burst the cell. The teacher could give an explanation as to how the pen is not selectively permeable for this “type of cell”. This demonstration can lead to a discussion about the cell membrane, the process by which materials enter the cell as well as, cell fluidity.
Grade: 8 General Science
Strand: Understanding Structures & Mechanisms – Systems in Action
Specific expectation: 2.5 use appropriate science and technology vocabulary, including organelle, diffusion, osmosis, cell theory, selective permeability, membrane, stage, and eyepiece, in oral and written communication.
3.2 identify structures and organelles in cells, including the nucleus, cell membrane, cell wall, chloroplasts, vacuole, mitochondria, and cytoplasm, and explain the basic functions of each (e.g., the nucleus holds all the information.
needed to make every cell in the body)
Quick Reply
