TEKS 4 B
Cellular Processes
TAKS Objective
– The student will demonstrate an understanding of living systems and the
environment.
TEKS Science Concepts 4 B
The student knows that cells are the basic structures of all living things and have specialized parts that
perform specific functions, and that viruses are different from cells and have different properties and
functions. The student is expected t
(B) investigate and identify cellular processes including homeostasis, permeability, energy
production, transportation of molecules, disposal of wastes, function of cellular parts,
and synthesis of new molecules
TAKS Objective 2
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Biology
For Teacher’s Eyes Only
Teacher Background:
The cellular membrane is a very complex, dynamic organelle. Because of its microscopic complexity and
dynamic ability, many of its abstract qualities (i.e. fluidity) have been difficult for students to grasp. The
cellular membrane is an organelle that is found in all living organisms whether they are prokaryotic (without a
nuclear membrane) or eukaryotic (with a nuclear membrane). Its structure is unique and assists the cell in
major functions such as transport, energy generation and synthesis of molecules.
Cell Membrane Structure:
The cell membrane primarily consists of a phospholipids bilayer and proteins dispersed throughout these two
layers.
Photo : www.che.vt.edu/Sum/images/cell-membrane.gif
Cell Membrane Function:
The primary function of the cell membrane is to maintain a barrier between the inside of the cell and the outside
of the cell. This barrier, however, is both semi-permeable and selectively permeable or has the ability to allow
some things to pass through while not allowing other molecules through. Second, the membrane acts to
transport these molecules across the membrane using the proteins dispersed across the surface (peripheral
proteins) and through the membrane. Most of the proteins that are used in transport typically span the whole
membrane (integral proteins), making contact with the outside environment and the cytoplasm. There are
three basic types of transport systems that the cell using to maintain homeostasis:

Passive Diffusion (No Energy) i.e. Osmosis – movement of water

Facilitated Diffusion (No Energy) i.e. Large Sugar Molecules (High to Low Concentration)

Active Transport (Uses Energy) i.e. Against Concentration Gradient (Low to High)
TAKS Objective 2
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Student Prior Knowledge
TAKS Objective 2
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Biology
5 E’s
ENGAGE
EXPLORE
Exploration 1
Semi-Permeability – Baggy and Iodine
Observation of both osmosis and facilitated diffusion across a semi-permeable membrane will occur during this
exploration. Students will observe a noticeable difference in color and water level and be able to deduce that
both water and iodine have crossed the semi-permeable baggy barrier. The less expensive the baggy the better
this experiment works.
Exploration 2
Eggactly What I Predicted
Diffusion/Osmosis – Egg, Karo® syrup and Distilled Water
Materials per student group:
2 Plastic Cups
Distilled or Tap Water
2 Eggs
Distilled White Vinegar
Plastic Wrap
Light Karo® syrup
1 Scale
TAKS Objective 2
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Biology
Preparation:
Prior to the actual experimentation 2 eggs for each group must be placed in each cup with enough vinegar to
cover the egg. The eggs must be left in the vinegar for at least 24 hours to dissolve the protective shell and
leave the cell membrane exposed. Cups may be reused once washed, rinsed and dried.
Student Materials:
1. Label the cups A and B
2. Place 100 mL of solution into each plastic cup as shown in the table below:
A
Distilled or Tap Water
B
Light Karo® syrup
3. Provide each student group with the following materials: 2 eggs with shell removed, 2 plastic cups
containing the above solutions, plastic wrap, 1 scale.
Student Activities:
Day 1
1. Carefully weigh both eggs and record their weight in Data Table
2. Now carefully place 1 egg in cup A and 1 egg in cup B.
3. Place cups in a safe area and do not disturbed for 24 hours.
Day 2
1. Obtain group eggs from stored location.
2. Use Data Table 1 to record observations of what happened to the weight of each egg as it was left in the
different solutions.
3. Complete the lab hand out, “Eggactly What I Predicted!”
TAKS Objective 2
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Biology
Exploration 3
Cell Membrane Manipulative
Materials per class:
Cell Membrane Manipulative
Magnets
Cell Membrane Student Worksheet
Preparation:
1. Order Cell Membrane Model (Science Kit Boreal®)
or Make Cell Membrane Manipulative
2. Place Magnets on the back of each part of the cellular membrane
3. Assemble Cell Membrane on Board
4. Copy student worksheet.
Student Activities:
1. Students will identify and discuss the different parts of the cell membrane that is represented on the
board.
2. The cell membrane will be disassembled and upon call, students will be required to place the cell
membrane back together and identify the structure with its function.
3. Independently students will label and describe the structures of the cell diagram in their worksheet.
Assessment:
Use the following rubric to determine whether the objectives have been met.
Points Earned
10 Points
8 Points
6 Points
0 Points
Diagram
All parts labeled
correctly.
Most parts labeled
correctly.
Some parts labeled
correctly.
No parts labeled
correctly.
Questions
All questions
were answered
reasonably.
Most questions
were answered
reasonably.
Some questions
were answered
reasonably.
No questions
were answered
reasonably.
TAKS Objective 2
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EXPLAIN
Exploration 1
Students will answer questions that follow the laboratory experience.
Exploration 2
Ask one student from each group to write the initial, final and change in weight data for both egg “A”
and “B” on the board. Have student graph class averages on the provided graph paper. Provide students some
time to analyze the data and make their conclusions concerning the experiment.
Now ask the students what they think happened to egg “A” and to egg “B.” Be certain that students
understand that only water was moving across the cell membrane of the egg. Begin to explain that the Light
Karo® syrup solution has fewer water molecules than inside of the egg. This therefore led to the egg loosing
water molecules to the syrup solution (high to low). Now ask the student to explain what they think happened
with egg “A.”
Now that the students understand the movement of water across the egg cell membrane, ask them what
they think would happened to the cell of a freshwater fish if it were placed in the ocean. The cells of the fish
would react the same way as the egg in the sugar solution. The fish cells would loose water and shrink. Ask
the students what would happen if a salt-water fish were placed in a pond. The cells of the salt-water fish would
react much in the same manner as the egg in distilled water or tap water; they would swell and potentially burst
open over time.
Exploration 3
Students will answer questions that follow the laboratory experience.
Exploration 4
Ask students to identify each of the cell membrane parts within the cellular membrane manipulative.
Explain the overall function of the cell membrane as being a boundary for the cell that has parts that act as
gatekeepers that allows molecules in and out of the cell. The cell membrane helps the cell to maintain a
balanced state or homeostasis.
Ask the student to describe the function of each of the identified parts and discuss their significance to
the cell. Revisit the different transport mechanisms that allow the cell to maintain homeostasis and how the
different types of proteins (channel, receptor, etc…) facilitate this transport. These mechanisms of transport
were covered in Learning Experience 1.
TAKS Objective 2
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ELABORATE
Elaboration 1
Cell Membrane Bubbles
Materials per group:
10 % Soap Solution – (100ml of Dawn® non-antibacterial liquid detergent to 1L of water)
500 mL of Light Karo® Syrup
2 Straws
80 cm piece of 100% cotton string
2 pieces of 100% cotton string of various sizes tied in to circles
Cafeteria-like tray
Plastic drop clothes to cover tables
Preparation:
Mix the soap solution and Karo® syrup before hand and place solution in trays for students. Then set up lab
stations with remaining materials at each station. Make copies of the student worksheet for each group or
individual.
Student Activities:
1. Students will work in groups of four. They will observe the dynamic state of the bubble and make
channel proteins that will allow materials to pass through the cell membrane.
2. Students will complete the lab worksheet.
Debriefing Procedures:
Ask students to name the different parts of the cell membrane. Students should be able to respond two layers of
fat and one layer of proteins. Ask the students to describe what part of the cell membrane simulation would
represent the fatty bilayer (bubble) and which part represents the proteins (cotton string loops). At this time you
can describe the components of the phosopholipid bilayer. The phospholipid bilayer consists of a phosphate
head that is hydrophilic (water loving) and two fatty acid tails that are hydrophobic (water fearing).
TAKS Objective 2
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Biology
Discuss why the cell has proteins in the membrane. The function of the proteins is to allow large molecules in
and out of the cell. Proteins are like gatekeepers, which only allow specific molecules to pass across the cell
membrane. This makes the membrane selectively permeable or semi-permeable. Ask the students to describe
the size of their simulated proteins and discuss the size of objects that they passed though the cell membrane.
Now ask the students if their proteins remained in the same place on their cell membrane. The proteins should
move around on the cell membrane. Use this to discuss the dynamic state of the membrane. The cell
membrane is very fluid and the phospholipids and proteins are always moving.
Lab Assessment:
Use the following rubric to assess student achievement of the learning objectives.
Points Earned
Questions
10 Points
8 Points
All questions have
been answered
reasonably.
Most questions have
been answered
reasonably.
6 Points
0 Points
Some questions have
been answered
reasonably
No questions have
been answered
reasonably.
Elaboration 2
Transport Flow Chart
EVALUATE
1. After engaging in exploration 2, the student will explain the process of osmosis as it relates to the transport
processes of the cell membrane to maintain homeostasis. A score of 5 on the rubric is required.
0 Points
3 Points
The student provides no
explanation or observations or the
explanations or observations are
incorrect.
5 Points
The student includes
only observations for
the explanation.
TAKS Objective 2
page 9
The student relates the
concept of density to the
formation of layers in the test
tube.
Biology
2. Upon completion of exploration 3, use the following rubric to determine whether the objectives have been
met. A score of 8 on the rubric is required.
Points Earned
10 Points
8 Points
6 Points
0 Points
Diagram
All parts labeled
correctly.
Most parts labeled
correctly.
Some parts labeled
correctly.
No parts labeled
correctly.
Questions
All questions
were answered
reasonably.
Most questions
were answered
reasonably.
Some questions
were answered
reasonably.
No questions
were answered
reasonably.
3. After completing the laboratory experience in elaboration 1, use the following rubric to assess student
achievement of the learning objectives. A score of at least 8 points is required.
Points Earned
Questions
10 Points
All questions have
been answered
reasonably.
8 Points
Most questions have
been answered
reasonably.
TAKS Objective 2
6 Points
0 Points
Some questions have
been answered
reasonably
No questions have
been answered
reasonably.
page 10
Biology
TAKS Objective 2
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Biology
Semi-Permeability Lab
Overview:
The primary function of the cell membrane is to maintain a barrier between the inside of the cell and the outside
of the cell. This barrier, however, is both semi-permeable (some things move freely back and forth across the
membrane) and selectively permeable or has the ability to allow some things to pass through while not
allowing other molecules through. Second, the membrane acts to transport these molecules across the
membrane using the proteins dispersed across the surface (peripheral proteins) and through the membrane.
Most of the proteins that are used in transport typically span the whole membrane (integral proteins), making
contact with the outside environment and the cytoplasm. There are three basic types of transport systems that
the cell using to maintain homeostasis:

Passive Diffusion (No Energy) i.e. Osmosis – movement of water

Facilitated Diffusion (No Energy) i.e. Large Sugar Molecules (High to Low Concentration)

Active Transport (Uses Energy) i.e. Against Concentration Gradient (Low to High)
I.
Define: Semi-permeability
II.
1.
2.
3.
4.
5.
6.
7.
Materials:
Iodine
Water
Starch
Beaker
Sandwich Bag
Graduated Cylinder
Glass stirring rod
III.
1.
2.
3.
4.
5.
6.
7.
Procedure:
Add 200ml of tap water to the beaker.
Add 20 drops of Iodine to the water in the beaker and record the color of the water.
Place 5 g of starch into the baggy.
Add 100 ml of water to the baggy with starch.
Zip the baggy closed. Mix. Record color of solution in baggy.
Place baggy into the beaker solution. Leave overnight.
Record color changes.
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IV.
Data:
Container
Substances in
Container
mL of Water
in Beaker
Before 24
Hours
mL of
Water in
Beaker
After 24
Hours
Color Before
24 Hours
Wait
Color After
24 Hour Wait
Beaker
Baggy
V.
Analysis/Conclusion:
1. Iodine is an indicator, what does and indicator do?
2. What macromolecule does Iodine indicate in solution?
3. Is the baggy semi-permeable?
4. How do you know?
5. Where did the starch go? (inside the baggy or outside of the baggy)
TAKS Objective 2
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6. How do you know where the starch went?
7. Where did the iodine go? (inside the baggy or outside of the baggy)
8. How do you know where the iodine went?
9. Why did the level of water change?
10. Where did the water go? Why?
11. How does this demonstrate semi-permeability in relation to the cell membrane?
12. What is independent variable?
13. What is the dependent variable?
TAKS Objective 2
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Eggactly What I Predicted!
Instructional Objective: After engaging in learning experience 1, the student will explain the process of
osmosis as it relates to the transport processes of the cell membrane to maintain homeostasis. A score of 5 on
the rubric is required.
Materials:
2 Plastic cups containing the liquids A and B
2 Eggs with shell removed
Plastic Wrap
1 Scale
Colorful Columns worksheet
Procedures:
Day 1
1. Label cup “A” and “B” with your group name or number.
2. Decide which egg is egg “A” and “B”
3. Weigh egg “A” on the scale and document its initial weight data in Data Table 1
4. Predict what you think will happen to the eggs weight when it is left in cup “A” for 24 hours. Record
the prediction in Data Table 1.
5. Place egg “A” into cup “A.” Cover the top of the cup with plastic wrap and set it aside.
6. Weigh egg “B” on the scale and document its initial weight data in Data Table 1
7. Predict what you think will happen to the egg “B’s” weight when it is left in cup “B” for 24 hours.
Record the prediction in Data Table 1.
TAKS Objective 2
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8. Place egg “B” into cup “B.” Cover the top of the cup with plastic wrap and set it aside.
Day 2
1. Carefully remove egg “A” from cup “A” and pat dry with a paper towel.
2. Now weigh egg “A” on the scales. Record the egg’s final weight in Data Table 1.
3. Carefully remove egg “B” from cup “B” and clean very carefully.
4. Now weigh egg “B” on the scales. Record the egg’s final weight in Data Table 1.
5. Calculate the weight difference. Record the weight difference in Data Table 1.
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Name________________
Egg Data Collection
Student Data Sheet
DATA TABLE:
EGG
INITIAL
WEIGHT
PREDICTION
FINAL
WEIGHT
WEIGHT
CHANGE
CLASS
AVG.
WEIGHT
CHANGE
A
B
Data Table 1
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ANALYSIS OF RESULTS:
1.
Develop a graph that represents that represents the data the class collected on the grid below.
Graph Title: _________________________________________________________________
CONCLUSION:
2. How do your predictions compare to your observations? Are they the same or different?
TAKS Objective 2
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Cell Membrane Model Manipulative
Name ___________________
Cell Membrane
(Student Worksheet)
We Need a Picture of the Cell Membrane for the students to label or we could have them draw their own cell
membrane and label the parts.
TAKS Objective 2
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Biology
Questions:
1.
List two functions of the cell membrane.
a.
b.
2. The cell membrane is composed of several materials. What are those materials?
3. Name four different types of proteins that are found in the cell membrane and give their function.
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Cell Membrane Simulation
Student Lab Sheet
Materials:
Tray with membrane solution
Plastic drop cloth to cover lab table
2 straws
80 cm piece of cotton string
2 cotton strings of various length
Student Data Sheet
Procedures:
1.
Cover table with the plastic drop cloth.
2. Place the tray with membrane solution on top of the plastic drop cloth.
3. Make a rectangle with the two straws and the 80 cm piece of cotton string. To do this feed the 80 cm
piece of cotton string through one straw and then through the other straw and tie the ends.
Straws
String
4. Now tie the other two pieces of cotton string into two different loop sizes.
TAKS Objective 2
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Loop
Two
Loop
One
5. Choose one person to be responsible for the rectangles, one person to be responsible for the loops, one
person to keep their hands dry at all times, and another person record data.
I.
Rectangle Group Member
II.
Loops Groups Member
III.
Dry Hands Group Member
IV.
Date Recorder Group Member
6. Group Member I must keep their hands completely WET at all times or they will pop the bubble. Place the
straw rectangle into the membrane solution and get the strings and straws completely wet.
7. Now make a bubble inside of the rectangle by gently lifting one side of the straw out of the solution and
then lift the other straw after a bubble has formed. If the bubble pops just make another.
8. Record your observations of the bubble. Are their colors? Do the colors stay in the same place or do they
move around the bubble.
9. Group Member II must get their hands completely WET and keep them wet.
10. Group Member II must now place the loops into the membrane solution and get them wet.
11. Now gently place the loops on the bubble.
12. Group Member III must now take a dry finger and pop the bubble INSIDE of the circular string.
13. Observe and record what happens. Does the inside of the loop have a bubble? Does the loop remain
stationary or does it move?
14. Group Member III and IV must now find different sizes of objects that can be passed through the
wholes inside the bubble.
15. Record the things that you placed through the different size wholes in the bubble.
TAKS Objective 2
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16. Group Member II must now gently place a finger inside one of the loops, drag it to the corner of the
bubble, and slide it off the bubble.
17. Record what happened.
18. Complete observation record and answer the questions on the lab worksheet.
TAKS Objective 2
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i)
Name____________________
Student Data Sheet
Membrane Observation:
1.
Describe the appearance and activity of first bubble inside the rectangle.
2. Describe what happened to the inside of the circular loops when a dry finger was placed inside of the
string.
3. Describe the loops activity on the bubble.
4. List the objects that were placed through each loop.
Large Loop
Small Loop
5. What happened to the bubble when the loop was carefully taken off the side?
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Summing up:
1.
What part of this activity simulated the cell membrane?
2. What side of the bubble would be the outside of the cell? Inside?
3. What part of the cell membrane allowed you to place different sizes of objects through the cell
membrane?
4. What part of the cellular membrane would the loops represent?
TAKS Objective 2
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Biology