Primary Type: Lesson Plan
Status: Published
This is a resource from CPALMS (www.cpalms.org) where all educators go for bright ideas!
Resource ID#: 48455
Small Cells verses Large Cells
The students will have an opportunity to discover that the size of cells (surface area and volume) has a major impact on the movement of nutrients
and waste products in and out through the cell by diffusion across the semipermeable membrane. The movement of these molecules is essential for
the health of the cell and to maintain homeostasis.
Subject(s): Science
Grade Level(s): 6
Intended Audience: Educators
Suggested Technology: Document Camera,
Computer for Presenter, Interactive Whiteboard, LCD
Projector
Instructional Time: 2 Hour(s) 30 Minute(s)
Freely Available: Yes
Keywords: volume, surface area, mitochondria, cell membrane, channel, cell, cube
Instructional Design Framework(s): Structured Inquiry (Level 2), Learning Cycle (e.g., 5E), Cooperative
Learning
Resource Collection: FCR-STEMLearn Cell Biology
ATTACHMENTS
Summative Assessment Rubric.docx
What Size is that Cell Lab Key.docx
What Size is that Cell Lab.docx
Independent Practice Interpreting a Model Answer Key.docx
Independent Practice Interpreting a Model.docx
Cell Model Rubric.docx
Cell Skit Rubric.docx
LESSON CONTENT
Lesson Plan Template: General Lesson Plan
Learning Objectives: What should students know and be able to do as a result of this lesson?
The students will be able to:
justify the benefit of small cell size to homeostasis.
correctly name and describe the function of the basic structures of the cell.
recognize, through the lab activity, that cell size is limited by distance from the cell membrane to the waste source.
recognize, through the lab activity, that cell size is limited by distance from the cell membrane to the organelle.
Prior Knowledge: What prior knowledge should students have for this lesson?
The students' prior knowledge should include:
parts of the cell and their function
how materials enter and leave the cell through passive and active transport
Guiding Questions: What are the guiding questions for this lesson?
page 1 of 4 How does the size of the cell affect the ability of materials to move into and out of the cell?
How does the cell size affect the transport of materials?
What is the difference between the cell's surface area and volume?
Teaching Phase: How will the teacher present the concept or skill to students?
The students will work in groups of four to complete each phase of the lesson. The students should be grouped by the teacher with prior student achievement in mind;
each team should have a high achieving student, middle achieving student, middle struggling student, and struggling student. The teacher should also consider
maturity and behavior factors.
The class will start with the following "grabber" question: "Think collectively with your group and write down your answer to the following: Name three examples of
school supplies where bigger is better."
The teacher will revisit prior knowledge about the cell through a short discussion (2-3 minutes) that refreshes knowledge about materials constantly entering and
leaving cells and the result of this action (growth, repair and health). Follow this line of reasoning to the question of whether being a bigger cell is better.
Announce that today the teams will complete a lab to investigate the sizes of cells. (See Guided Practice for instructions.) Students will begin the lab activity; during
the wait segment, the students will work on an independent practice assignment.
Note: During the independent practice, the students will work in pairs: high achieving with middle struggling, and middle achieving with struggling student. Once the
independent practice is completed, they will return to the lab to finish with the agar blocks and answer the question from the lab activity with their team.
The students are called back together with the teacher to pull together their experiences from both the lab and the independent practice assignment.
Guided Practice: What activities or exercises will the students complete with teacher guidance?
The lab handout for student use is attached, and an answer key has also been provided for teachers. The lab procedures are included in the handout.
The teacher may wish to display part or all of the lab handout with a projector.
Lab: What Size is that Cell?
Materials and apparatus:
bromothymol blue agar block
plastic knife
disposable gloves
ruler
plastic cups
household white vinegar
colored pencils
Procedure:
1. Work with your team and perform tasks according to your assigned roles. The team member handling the materials will put on the disposable gloves.
2. Place the bromothymol blue agar block on a paper towel. Use your ruler to measure a cube that is 1 cm on each side. Cut the cube with the plastic knife. Put the
cube in the plastic cup.
3. Go to your data sheet. In first row of the first column, use your ruler to draw a square with 1 cm sides. Color the square blue and label the square "before."
4. Use the plastic knife to cut another cube from the remaining bromothymol blue agar block that is 2 cm on each side. Put the cube in the plastic cup and pour in
enough vinegar to cover both bromothymol blue agar blocks.
5. Go to your data sheet. In the second row of the first column, use your ruler to draw a square with 2 cm sides. Color the square blue and label the square "before."
6. Allow the plastic cup to sit on your table for 30 minutes.
7. After 30 minutes, put the disposal gloves back on and gently remove the two blocks from the vinegar.
8. Pour the vinegar down the drain. Gently rinse the blocks under running water.
9. Set the blocks on paper towels. Your teacher will demonstrate how to use the plastic knife to remove a slice from the center of each block.
10. Use your ruler to measure the distance from the edge to the start of the blue color. This is the distance the vinegar diffused into the bromothymol blue agar cube.
11. Go your data sheet. Draw another square of 1 cm on each side and label it "after." Color the square appropriately and label the distance that the vinegar diffused.
12. Repeat steps 10 and 11 with the 2 cm cube.
13. After you finish items 1 and 2 on the data sheet, call your teacher over to check you work.
14. Clean up: Only proceed on to clean up after receiving your teacher's check.
Rinse and dry the cups and knife.
The agar material goes in the trash.
Tide up the work space by grouping all materials in the middle.
Wipe down the work space with a wet paper towel.
Independent Practice: What activities or exercises will students complete to reinforce the concepts and skills developed in the
lesson?
While the cubes soak in the vinegar, the students will work in pairs to complete the Interpreting a Model worksheet. An answer key has been provided.
Closure: How will the teacher assist students in organizing the knowledge gained in the lesson?
After the completion of the lab and the Interpreting a Model questions, the teacher will bring the class together to tie their ideas and experiences together. First,
review the lab. Let the students help you retell the sequence of events.
In the lab, the agar blocks represented two cells with different volumes.
The lab simulated nutrients entering through a semipermeable membrane by using vinegar.
If the cell mitochondria are located around the center of our simulated cell, then we are concerned with getting the nutrients to the mitochondria.
The students measured the distance that the nutrients (vinegar) traveled to get to the center of each cell (block) where the mitochondria would be located.
At this point, use the clicker questions.
1. Which cell showed that the vinegar had a shorter distance to travel to the mitochondria?
A. Smaller cell
page 2 of 4 B. Larger cell
Answer: A
2. Which cell would the best chance of survival?
A. Smaller cell
B. Larger cell
Answer: A
The teacher will lead a class discussion on why small cells have the best chance of survival over large size cells. Tie in the independent practice activity, where
students examined the cell membrane with its channels that are the actual site for diffusion across the cell membrane. Let the students help to tell the sequence of
events.
Return to the clicker questions:
3. Would nutrient molecules be able to reach the mitochondria faster if the cell had a larger or smaller volume?
A. smaller volume
B. larger volume
Answer: A
4. Based on the answer to the previous question, why are small cells a very good idea?
A. cuter
B. cheaper
C. nutrients do not have to travel as far to the mitochondria
D. nutrients travel farther to the mitochondria
Answer: C
After the teacher has finished the clicker questions and discussed the answers with the students, the students will be given the exit question below to answer and turn
in to the teacher.
Exit Question:
Write three good sentences justifying why we, as very large organisms, have so many small cells that make up our bodies.
Summative Assessment
Working in teams of four, students will develop a skit or 3D model that will demonstrate the advantages small cells have over large cells. If students develop a skit:
Each of the four students on the team must have a part.
The cells must have a cell membrane, mitochondria, nutrients, and carbon dioxide.
Two cells must be developed with an obvious difference in volume.
Each cell membrane must have channels that demonstrate diffusion.
Each cell part must be labeled.
The team must have a written justification that explains the advantages small cells have over large cells in terms of volume and surface area, plus the benefits to
overall health and maintenance of the cell.
They should include three good sentences.
The project should be neat, organized and turned in on time.
A general Summative Assessment Rubric has been provided, as have rubrics designed specifically for the Cell Skit and Cell Model assignments.
Formative Assessment
Guided Practice:
1. The teacher will circulate around to the groups with the following questions in mind as students finish cutting the agar blocks. Students will be asked questions
individually while they are involved with the hands-on activity. Sample questions:
Describe the difference between the two agar blocks using the terms "volume" and "surface area." (Students may not know very much about surface area. Remind
them that area is length times width of each side and volume is amount of space it takes up.)
Without using numbers, compare volume to surface area of the two agar blocks. (Allow students to make predictions.)
How is the agar block like the cell? (it has a boundary, takes up space, semi-solid)
2. During Guided Practice, the lab instructions frequently direct the students to call the teacher to their lab table to have their work checked.
3. The teams should answer the following two-part questions, write down their prediction, and turn that paper in to the teacher. The students will revisit these
responses during the closure.
a. Ask the students to make predictions about the molecules that enter and leave individual cells in regard to the growth and well-being of the cell. Then ask them to
think about their answer in relation to the "grabber" question. ("Think collectively with your group and write down your answer to the following: Name three
examples of school supplies where bigger is better.")
b. What is the alternative if bigger is not preferred in cells? (many small cells)
Closure:
During Closure, the teacher will end the day with an exit question for students to answer individually. Students will use clickers or interactive signal responses to
respond to multiple choice questions.
Feedback to Students
As the teacher questions students about their understanding of the cell as it relates to the agar block, he or she will give direct feedback through praise or
redirected questions.
Clicker questions: The results will be projected on the board and discussed immediately.
During the lab, the students are directed to ask the teacher for feedback frequently. The teacher check-off section is built into the data table.
ACCOMMODATIONS & RECOMMENDATIONS
page 3 of 4 Accommodations:
Maintain high expectations and a structured environment.
Use pictures where appropriate, and repeat/rephrase/slow down when giving explanations and instructions.
Offer extra time on an activity.
Always enhance teaching by modeling of learning strategies.
Extensions: One extension to this lesson would involve introducing a mathematics standard to allow the students to calculate surface area and volume. This would
introduce the opportunity to compare ratios of surface area to volume, and introduce a new factor to consider when justifying that small cells are better at moving
materials than larger ones.
Suggested Technology: Document Camera, Computer for Presenter, Interactive Whiteboard, LCD Projector
Special Materials Needed:
Materials needed for agar blocks:
20 grams of agar
1000 grams deionized water (if available)
0.1 grams bromothymol blue powder
To prepare the agar blocks:
Mix the three together over low heat, stirring constantly until agar is dissolved.
Additional bromothymol blue may be added in very small amounts to adjust blue color.
Pour the mixture into a flat-bottomed rectangular pan to cool.
The vinegar used is plain white vinegar from the grocery store.
Further Recommendations:
The teacher should be mindful of the age of the students and their handling of the agar blocks.
Review the safety standards and agreement with students.
Follow the MSDS guidelines for bromothymol blue dye.
Additional Information/Instructions
By Author/Submitter
This lesson plan supports part D of standard SC.6.L.14.3.
SOURCE AND ACCESS INFORMATION
Contributed by: Myra Crews
Name of Author/Source: Myra Crews
District/Organization of Contributor(s): Bay
Is this Resource freely Available? Yes
Access Privileges: Public
License: Attribution-NonCommercial 3.0 Unported
Related Standards
Name
SC.912.L.14.2:
Description
Relate structure to function for the components of plant and animal cells. Explain the role of cell membranes as a highly
selective barrier (passive and active transport).
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