Investigating Factors That Affect Cell Membrane Permeability
Bard High School Early College, Manhattan
Summer Research Program for Science Teachers
Course: Living Environment (Biology)
Grade Level: 9th and 10th Grades
Unit: Cell Structure and Cellular Transport
Purpose: Students investigate factors that affect the integrity of cell membranes. Beet tissue will be used as the model to investigate the types of environmental stresses that affect membrane integrity.
Students will be able to (SWBAT):
· Understand the fluid-mosaic model of membrane structure.
· Explain the function of the cell (plasma) membrane.
· Differentiate between semi-permeable and selectively permeable membranes.
· Understand the different ways in which materials are transported across the cell membrane and how the structure of the cell membrane makes this possible.
· Determine the types of molecules that can pass across cell membranes.
· Determine the factors that affect membrane fluidity and permeability.
· Formulate a hypothesis about the environmental factors that will alter the permeability of the cell membrane.
· Design an experiment to test their hypothesis.
· Collect and analyze data as well as draw valid conclusions from data.
· Present their experimental findings to the class by creating a poster.
Students will have an understanding of the four classes of biologically important compounds (ie. carbohydrates, fats, proteins and nucleic acids). This laboratory activity follows a “cookbook” experiment in which students will learn how to use a spectrophotometer to determine the concentration of known and unknown samples.
1. 8 fifty minute class periods
a) 3 class periods to explore the structure and function of the cell membrane and types of cellular transport.
b) 2 class periods to formulate a testable hypothesis and design an experimental procedure
c) 2 class periods to conduct the inquiry based lab activity.
d)1 class period to present data and results to the class.
1. How would you describe the structure of the cell (plasma) membrane?
2. What is the function of the cell membrane?
3. Why is the cell membrane said to be “selectively permeable”?
4. What are the different ways in which materials can pass across the cell membrane?
5.What factors affect the fluidity or permeability of cell membranes?
Preparation and Procedure:
Part 1 Materials:
· K-W-L worksheet for each student on structure of plant and animal cells and cell membranes
· WebQuest Worksheets for cell membrane structure and function and cellular transport
· Print copies of websites used for the WebQuests
· Laptop computers with Internet access
· LCD projector
· Overhead projector
· Newsprint or an overhead projector and transparencies to record student responses to the K-W-L worksheet.
Part 1: - WebQuests (3 class periods)
1. Students will complete a K-W-L chart on cell structure.
2. Students will work in groups of two or three to complete WebQuests that explore the
a) structure and function of cell membranes
b) factors that affect fluidity and permeability of cell membranes.
c) various ways materials enter and leave the cell.
3. Use the Essentials Questions to guide students during the WebQuest.4. Students will work in groups of two or three to formulate potential experimental questions to test various factors that affect cell membrane permeability. Experimental questions will be posted on either newsprint or an overhead transparency.
a) Membrane Structure: Demo Tutorial: http://www.bio.davidson.edu/people/macampbell/111/memb-swf/membranes.swf
b) BioCoach Activity – Biomembranes I: Membrane Structure and Transport: http://www.phschool.com/science/biology_place/biocoach/biomembrane1/intro.html
c) Interactive Concepts in Biochemistry – Interactive Animations: Cellular Transport: http://www.wiley.com/legacy/college/boyer/0470003790/animations/membrane_transport/membrane_transport.htm.
d) Cell Membrane: Just Passing Through: http://www.teachersdomain.org/asset/tdc02_int_membraneweb/
e) Cell Biology Animation – John Kyrk: Cell Membrane: http://www.johnkyrk.com/cellmembrane.html
2. WebQuest Resources:
a) WebQuest.Org: http://webquest.org/index.php
Website that describes how to develop and implement a WebQuest in the classroom.
Part 2: Inquiry Based Lab Activity (5 class periods)
test tube rack
test tube holder
10 mL graduated cylinders
Cork borer with 4 or 6-mm inside diameter
Beets (canned or fresh)
Wash bottle with deionized water
Scalpel or razor blade
Newsprint for presentation of results
Beet tissue will be used as a model to investigate how temperature and/or various alcohols affect cell membrane integrity. Beet cells contain a red pigment called betacyanin located in the tonoplast. Betacyanin, a water-soluble pigment, cannot pass across the membrane of the tonoplast or cell membrane of the beet cells as long as these membranes remain intact. If however, these cells are exposed to changes in temperature or a lipid soluble solvent like ethanol, the integrity of the cell membrane becomes compromised. As a result, betacyanin can leak out of the cells and into the surrounding water. The extent of the damage to the cell membrane is directly related to the intensity of red color that appears in the water surrounding the beet. The intensity of the red color can be quantitatively assessed using a spectrophotometer. Students will be expected to incorporate the use of the spectrophotometer into their experimental design to measure the intensity of color in the surrounding environment. The intensity of color should be proportional to the amount of damage sustained by the beet cell membrane.
1. Students will work in groups of two or three to:
a) formulate a hypothesis to answer one of the experimental questions posed by the class at the end of Part 1.
· Once the instructor has approved their hypothesis, the students in the group will begin to discuss an experimental procedure to test their hypothesis.
(1) Homework: Students will complete their procedures at home. Students may conduct research using the Internet in order to design their procedure.
b) Students will review each other’s procedures in class before deciding on a final procedure to submit to the instructor for approval.
2. Once the instructor has approved the procedure students will carry out their experiment during their assigned laboratory period.
3. The students will be given time during the class period following the laboratory activity to summarize their data and present their results to the class using newsprint or overhead transparencies. Students will also be expected to complete the “L” section on the K-W-L worksheet.
4. Teacher Preparation for Part 2:
a) Possible experimental procedures for this laboratory activity can be found by reviewing the following:
· Lab #2: Stress and Cellular Membranes
(1) University of Vermont - www.uvm.edu/~bio1and2/lab/Lab manuals Fall 2005/Lab 2 Membranes.doc
· Effects of Temperature and Solvents on the Cell Membrane
(1) Science on the Move – Marist College: http://library.marist.edu/sotm/word/B14Cellmembrane.doc
Suggestions for Assessment:
· Evaluate the completion of the WebQuest worksheets.
· Evaluate the “L” column for the K-W-L worksheet.
· Evaluate the group presentation of data and results.
· Evaluate a formal laboratory report submitted at the completion of the laboratory exercise.
National Science Educational Standards:
1. National Science Educations Standards – Grades 9 to 12
a) Science as Inquiry:
· Abilities necessary to do scientific inquiry
· Understandings about scientific inquiry
b) Life Science:
· The cell
c) K-12 Unifying Concepts and Processes:
· Evidence, models, and explanation
· Change, constancy, and measurement
· Evolution and Equilibrium
New York State Standards:
1. Standard 1: Students will use mathematical analysis, scientific inquiry, and engineering design, as appropriate, to pose questions, seek answers, and develop solutions.
a) Key Idea 1 - The central purpose of scientific inquiry is to develop explanations of natural phenomena in a continuing and creative process.
· Performance indicators 1.1, 1.2, 1.3
b) Key Idea 2 - Beyond the use of reasoning and consensus, scientific inquiry involves the testing of proposed explanations involving the use of conventional techniques and procedures and usually requiring considerable ingenuity.
· Performance indicators 2.1, 2.2, 2.3, 2.4
c) Key Idea 3 - The observations made while testing proposed explanations, when analyzed using conventional and invented methods, provide new insights into natural phenomena.
· Performance indicators 3.1, 3.2, 3.3, 3.4, 3.5
2. Standard 4: Students will understand and apply scientific concepts, principles, and theories pertaining to the physical setting and living environment and recognize the historical development of ideas in science.
a) Key Idea 1 - Living things are both similar to and different from each other and from nonliving things.
· Performance indicator 1.2