The Structure and Function of Cells: Making Biology Fun
Investigate life below a microscope and discover the world of plant and animal cells.
By Bruce Howard
At the middle school level, we are interested in learners being able to distinguish between the basic structures and functions of plant and animal cells. As they move into higher grades, they must be able to make observations and describe the structure and function of organelles found in plant and animal cells, summarize how the different levels of organization are integrated within living systems, and describe the function of different organ systems and how they enable complex multi-cellular organisms to survive.
What's the Difference?
So what are the key differences in structure and function of plant and animal cells? Most notably, plant cells have a cell wall made of cellulose and are typically larger, with a more well-defined shape. Animal cells have smaller, irregular shapes with a plasma membrane but no cell wall. In terms of organelles, plant cells have a large central vacuole and plastids, while animal cells have centrioles and a centrosome.
But perhaps most notably (and key to teaching here at the 4-6 grade level), plant cells have chloroplasts. Chloroplasts contain the chlorophyll which is so vital in photosynthesis. Animal cells do not have chlorophyll and do not help in photosynthesis.
Middle schoolers are concrete-operational learners. That is, they understand about the world around them in very concrete, visual, observable ways. It is important to begin with what they know, and can observe, before moving them along into the more abstract world of cell structures and their functions.
Observe, Observe, Observe!
Your pupils already have a well-developed sense of the natural world around them. Capitalize on this. Provide an anchor point by having them begin with some observations. When they are outside on the playground or in a nearby field/ forest, have them spend a few minutes recording all the plants and animals they can see. If they are familiar with it, they can identify specific names using a field guide or other reference book. Upon returning to the classroom, ask them to get into cooperative groups and name as many differences as they can think of between plants and animals. Repeat this exercise listing similarities instead of differences.
Next, discuss what plants and animals DO differently, and what structures or functions their various body parts may serve. Use that discussion to ease into the notion of similarities and differences at the cellular level:
- Both plants and animals are living systems. Use this moment to reinforce what is alive, what is not alive, and characteristics of life. Contrast plants and animals with non-living items like rocks, clouds, water, and pizza.
- Provide a list of items for classification: corn stalk, gerbil, ear of corn, gerbil poop, algae, bacteria. Explain why each is considered a plant, animal or non-living item.
- Conduct a lab where you examine various specimens under the microscope, starting with similarities and differences between various structures they see (cell walls and shapes, nucleus). Your young scientists can try to classify them as plant or animal. Then you provide a few answers and some guidance.
- After completing one or two of the lessons below, come back to the lab and have them identify the organelles. Follow up with an explanation of functions.
The lessons or activities below should help you to convey these concepts and set a foundation for more in-depth teaching on the subject in later grades. At the fifth grade level, I highly recommend you do not spend much time on these. I suggest you merely establish the basic knowledge that cells exist, and that plant cells are different from animal cells because of photosynthesis.
If you want to spend some time in the computer lab, this website contains several gems you will want have your class explore, primarily the interactive cell model. I suggest that you review this site in advance and choose only a couple of pages for your class to visit, as not everything here is of great value.
This site provides teacher background knowledge and worksheets for use while building a cell model. It focuses on the cell organelles in both plant and animal cells. In addition to the provided plan, there are links to animated cells and other material for enrichment. It also includes assessment materials and is easily adapted for use with fifth to seventh graders.
Here is a video featuring a teacher who has created graham cracker-based edible cells using licorice, vanilla wafers, icing and M&Ms. The teacher walks you through the procedure. For assessment ideas, written worksheets, or more detail, visit the Alabama Learning Exchange.
If icing is not your fancy, here are two very well-crafted lessons which walk you through creating cells using Jello and other tasty treats. Both this lesson and the WikiEducator's "Cell-O" lesson provide a basic study of the animal and plant cell characteristics and their functions. Pupils make a replica of a cell using Jell-O and get an edible representation of a 3-D version of a cell. Provides guidance for using a few different Internet resources.