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6-8 > Microscopic World
Grade level: 6-8 Subject: Microscopic World Duration: Two class periods
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Students will:
1. describe the cell as a three-dimensional object;
2. compare and contrast a plant cell and an animal cell; and
3. describe and locate the cell organelles within the cell.

For this lesson, you will need:
Yellow gelatin—one small box per two students. (Although any color can be used, yellow will allow the students to view the interior of the product more clearly.)
Knox gelatin—one envelope per two students. (Just the gelatin—without water—will be added to the yellow gelatin to create a firmer substance.)
Quart-sized plastic bags
Twist ties
Boiling water
Mixing bowls
Disposable plastic sandwich containers
Various canned fruits: plums, mandarin oranges, grapes, and so on
Pepper, yarn, pencil shavings, plastic bubble packing

1. Review what you know about cells with the class. Find a good diagram of a cell, label each organelle, and discuss the function of each. Explain that although all cells from living things share some common characteristics, cells from plants and animals have important differences. Tell students they will be making their own plant and animal “cells” to understand the differences in their structures.
2. Using the recipe on the package, prepare the yellow gelatin to a liquid state. Then add the contents of the Knox plain gelatin envelope—without any extra water—to the yellow gelatin. This will create a firmer substance.
3. Divide students into partners. Give each group two plastic bags, one plastic sandwich container, warm liquid gelatin, and assorted fruits.
4. Have students put one plastic bag in a plastic container as a liner and one plastic bag opened on the desk. Explain that the plastic bag represents the cell membrane and the plastic container represents the cell wall. Since plant cells have sturdy cell walls, the lined plastic container represents a plant cell. The plastic bag opened on the desk represents an animal cell.
5. Have students place similar amounts of gelatin in each plastic bag. Next, have them add fruits to represent different parts of the cell: use grapes for chloroplasts, mandarin oranges for mitochondria, plums for nuclei. Add smaller materials to represent other parts of the cell: pepper for ribosome, plastic bubble wrap for vacuoles, yarn for endoplasm reticulum, and pencil shavings for chromosomes.
6. Finally, close your plastic bags, or “cells,” with twist ties and refrigerate to set. The next day, study your two cells and note the structural differences between your plant cells and animal cells. What are their shapes? What effect does the cell wall have on the plant cell? Why do you think plant cells have sturdy walls? How does this help them survive? How does this influence the structure of the plant itself? Why don’t animal cells need cell walls? Upon completion of the discussion students should understand that in the animal cell, the membrane controls what can enter or leave the cell. It lets in useful substances and lets out waste. An animal’s cell must take in food to survive. In contrast, the plant’s cell must make its own food from sunlight, carbon dioxide, and water. The plant’s cell wall, made of a substance called cellulose, is tougher and thicker than the cell membrane. Cellulose is only found in the plant cells and is used for protection and support.
7. Next, form a plant “tissue” by stacking a few of the plant cells created by the class. Have the students compare the structural and overall shape differences. This can be done individually as well as after stacking them to form tissues.
8. Optional: Create a slide of a plant cell and compare a real image of plant cells to your model. Ask students to compare the plant 3-D models to the brick wall-like structure that they see under the microscope.
9. After a discussion, have the partners create a chart that compares the animal and plant cells. When they’ve completed their charts, have partners present their lists with the class. Create a complete class chart with everyone’s findings.
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Adaptation for older students:
A challenging project for older students would be to research and design a traveling Cell Museum. After conducting research on a particular type of cell, students can use self-hardening modeling clay to create 3-D models for specific cell structures. A museum guide should be developed to support the display.
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Discussion Questions

1. Why are cells called life’s building blocks?
2. Compare and contrast plant cells and animal cells.
3. How has technology played an increasingly important role in our knowledge of cell structures?
4. Cells do not exist on their own in many forms of life. Instead, they form small parts of larger organisms. What are the advantages to this approach to life?
5. Describe how each cell is like a microscopic factory. Use details of organelle function to support your description.
6. Analyze and debate the ethical issues that have arisen out of the study of cell biology: cloning, gene therapy, test-tube babies, DNA fingerprinting, and genetic engineering.
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Have each set of student partners develop three questions about cells that could be answered by using their model. Sort and combine the questions into one evaluation tool that can be used by the entire class for an assessment on cell structure.
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Hot off the Presses:CELL
With 10 trillion cells in the human body, your student publishers will have no problem with subscription numbers! Provide a new format for reporting on cells by dividing your students into teams of editors, writers, publishers, and artists to create a new publicationby cells and for cellsthat will creatively answer all kinds of questions about cells and microbiology. Questions could relate to common misconceptions of cell biology (are cells dynamic or static?) or the impact of DNA research on court cases. Have your students compose a magazine that combines current information about the world of microbiology with creative and innovative ideas for advertising and articles. The magazine can be hand drawn or published on the computer depending on your resources in the classroom. Either way, there is great potential for an inspiring project that will integrate art, writing, and science!

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Suggested Readings

The Life of a Cell
Andres Llamas Ruiz. Sterling, 1997.
From single-celled organisms to the complexity of the human body, the cell is the basic unit of life. This highly illustrated book takes a look at the various parts that make up a cell, how a cell functions, and how cells adopt a specialty as they gather together to form tissues.

Cells: Amazing Forms and Functions
John K. Young. Franklin Watts, 1990.
Along with basic information about the structure and function of cells, this book provides details about the variety of strange and wonderful types of cells that make up the human body. It also includes a brief history of our understanding of DNA, the "code of life."

Cloning: Frontiers of Genetic Engineering
David Jeffris. Crabtree Publishing, 1999.
Astonishing new findings about cells, DNA, and genetics are leading to rapid advances in the treatment of disease, the success of organ transplants, and the efficiency of agriculture. Succinct text, photographs, and illustrations explain the history of genetic research and the potential of cloning to our future.

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Cells alive!
Cell models, challenges, great images, and links to websites on cells

Microscopes, Cells, DNA, and You
Lesson plans, activities, and links on cells

Cell Biology Topics
Lots of information on the parts of a cell

Biology Book Online - Cells II Cellular Organization
Text and great graphics of cell parts and their functions

I Can Do That - Cells
Fun - elementary, yet accurate info and cartoons about cells

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Click on any of the vocabulary words below to hear them pronounced and used in a sentence.

speaker    DNA
Definition:The part of a cell that contains a code that controls the way a cell works.
Context:DNA, deoxyribonucleic acid, is found in chromosomes.

speaker    mitochondria
Definition:The part of a cell that releases energy through a process called respiration.
Context:All cells contain tiny energy stations called mitochondria.

speaker    mitosis
Definition:The splitting of a cell’s nucleus into two parts.
Context:New cells are made by division. One form of cell division is mitosis.

speaker    nucleus
Definition:The part of the cell that carries its genetic information and controls everything that the cell does.
Context:The heart of every animal cell is the nucleus.

speaker    organelles
Definition:The internal structures of a cell.
Context:The organelles allow cells to live by harnessing energy and putting it to work.

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This lesson plan may be used to address the academic standards listed below. These standards are drawn from Content Knowledge: A Compendium of Standards and Benchmarks for K-12 Education: 2nd Edition and have been provided courtesy of theMid-continent Research for Education and Learningin Aurora, Colorado.
Grade level:6-8
Subject area:Science
Knows the general structure and functions of cells in organisms.
Knows that all organisms are composed of cells, which are the fundamental units of life; most organisms are single cells, but other organisms (including humans) are multicellular.

Grade level:6-8
Subject area:Science
Knows the general structure and functions of cells in organisms.
Knows that cells convert energy obtained from food to carry on the many functions needed to sustain life (e.g., cell growth and division, production of materials that the cell or organism needs).

Grade level:6-8
Subject area:Science
Knows the general structure and functions of cells in organisms.
Knows the levels of organization in living systems, including cells, tissues, organs, organ systems, whole organisms, and ecosystems, and the complementary nature of structure and function at each level.

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Wendy Goldfein, teacher, Fairfax County Schools, Virginia, and freelance curriculum consultant.
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