Download Science Lesson Plan Biology 111/112 Unit 1 – The Cell Cell

Science Lesson Plan
Biology 111/112
Unit 1 – The Cell
Cell Membrane
Kate Whitters
February 14th, 2013
EDUC 5883
Outcomes covered:
Knowledge:
Biology 111/112 (314-8) - It is expected that students will:
Explain how materials are able to move into and out of cells through a selectively permeable
membrane.
Include:
 fluid mosaic model
 passive transport – osmosis, diffusion and facilitated diffusion
 active transport – molecular transport, endo- and exocytosis
Attitude Outcomes:
445 - work collaboratively in planning and carrying out investigations, as well as in generating and
evaluating ideas
Assumptions:
1. Students have been working through Unit 1 – The Cell for several weeks now. By preparing
and observing slides of human cheek cells, students have identified many of the major
organelles. Through class discussion, they have created a model of the cell as a factory.
2. Students have been practicing open class discussions since the beginning of the course.
Incoming Knowledge of Unit:
From their prior courses in science, students should be aware that the cell membrane, or plasma
membrane, is a semi-permeable “envelope” which encases the cell.
From their experience in chemistry, students should have a working knowledge of polarity. This
should include knowledge that polar molecules prefer to interact with polar molecules, and will not
interact with non-polar molecules. This will lead into a discussion on hydrophilicity and
hydrophobicity.
Further direction:
Next class, students should revise their definitions of the Fluid Mosaic Model as they gain new
information on the structure of the membrane, as well as the function of the embedded proteins.
Groups should work to develop presentations which highlight and explore the essential features of
the Fluid Mosaic Model.
Title of Lesson: An Introduction to the Fluid Mosaic Model
Curriculum Outcome: (314-8) - It is expected that students will:
Explain how materials are able to move into and out of cells through a selectively permeable
membrane.
Include:
 fluid mosaic model
 passive transport – osmosis, diffusion and facilitated diffusion
 active transport – molecular transport, endo- and exocytosis
Attitude Outcomes:
445 - work collaboratively in planning and carrying out investigations, as well as in generating and
evaluating ideas
Learning Objectives:
Assessment (Products):
1. Students should have a working knowledge of the Fluid
Group definitions (draft) of the Fluid
Mosaic Model of the cell membrane, which should include:
Mosaic Model
Group proposal for “Fluid Mosaic
 lipid bilayer made of amphiphilic phospholipid
Model” project design
molecules
 embedded proteins for the purpose of transport,
signaling, and structure
Time Required for this lesson: 1 lesson (40 minutes)
Materials/ Resources
Tide to Go
T-Shirt
Olive Oil
Basin
Water
Methods / Structure:
Students in small groups (4-6). All students able to see the SMART board easily from where they are
sitting.
Instructional Strategies/ Procedure for the Class:
Warm Up: Greasy Mess (15 minutes)
Purpose: to introduce the concept of amphiphilicity
Big Question: How does soap work?
Bring in an old t-shirt and splash some oil on it. Use Tide-to-Go on half the stain, then wash in the
water basin. Show students that the half which had been treated with Tide washes almost clean, where
the side which was cleansed only with water remains stained.
Question class: How might soap work? Why does it do a better job cleaning than just water? Reserve
judgment on responses.
Show the following YouTube video illustrating how soap works:
http://www.youtube.com/watch?v=ga2ff1nO0uo
Request a summary of the video from students. What two ways does soap work to remove dirt?
Class discussion should be focused on two ways in which soap works to clean:
1. It is a surfactant
What is a “surfactant?” A surfactant reduces the surface tension of water.
How does this help in the removal of dirt? Students will provide a variety of answers. Conversation
should be guided to settle on the fact that the reduction of surface tension allows water to surround
molecules of dirt more effectively, breaking them up.
2. It forms soap micelles around the dirt molecules
What are soap micelles? Soap molecules form “bubbles” around the dirt molecules, allowing water to
wash them away
What property of the molecules in soap (formed during saponification) allows them to form soap
micelles?
They have parts that are hydrophilic (water-loving), and parts that are hydrophobic (water-hating).
Scaffold academic language by asking for a word which may mean water-loving and water-hating (use
“amphibian” as an example). The class should be exposed to the term “amphiphilic”.
In terms of amphiphilicity, how do soap micelles form?
The water-hating (hydrophobic) heads face in toward the dirt molecule. The water-loving tails
(hydrophilic) point out. When the dirt molecule is surrounded, the micelle is washed away by water,
removing the dirt.
Students should remember the concept of amphiphilicity, as it will be important later in the lesson.
Cell membrane discussion (20 minutes)
Show the slide of the cheek cell we have been focusing on over the course of the unit.
Low cognitive demand question: What is the structure around the margin of the cell?
Plasma or cell membrane.
Group Brainstorm (3 minutes)
Why do cells need membranes? What functions does it perform?
If groups have compiled what they feel is a comprehensive list, they may move on to a discussion
focused on creating an analogy for the membrane which fits with our model of the cell as a factory.
A class discussion should ensue, requesting groups share their lists of membrane functions. Important
functions to include are:
1. keep the overall structure of the cell
2. keep things in (i.e. the cytosol)
3. keep things out (i.e. toxins, excess water)
4. movement (show the Amoeba video if necessary: http://www.youtube.com/watch?v=7pR7TNzJ_pA)
So the primary function of the cell membrane is regulate movement of material in and out of the cell.
What kinds of things move across the membrane?
Wastes, nutrients, water, etc.
Can anything move across the membrane?
No, the membrane can choose what goes across. It is selectively permeable.
What would be the function of the cell membrane in relation to our factory model?
Students should work together to generate a model. One example would be the security system, which
allows some people entrance but not others. This model will be refined next class, and should not be
explored in too much detail.
What might this semi-permeable membrane look like?
Because of the movement of the amoeba, we know it’s not stiff. It must be fluid.
Move the class toward a discussion of organic molecules. During warm-up, we saw organic molecules
which spontaneously arranged themselves around a molecule of dirt. These amphiphilic molecules
could also form a membrane spontaneously.
The membrane is made primarily of phospholipids, which have a hydrophilic phosphate “head”, and
two hydrophobic lipid “tails”.
Invite a student to come to the board and draw a membrane made of phospholipids.
If they draw a single layer of phospholipids side-by-side, discuss the make-up of cells and their
surroundings. Students should know that they are both composed primarily of water. Guide the
discussion to end with the membrane as a “phospholipid bilayer”, with hydrophilic heads pointing out,
and hydrophobic tails interacting with each other.
The rest of the discussion should quickly introduce the concept of proteins in the membrane.
We know that the membrane is “selectively permeable”, how do molecules move across?
Instructional Strategies/ Procedure for the Class:
Warm Up: Greasy Mess (15 minutes)
Purpose: to introduce the concept of amphiphilicity
Big Question: How does soap work?
Bring in an old t-shirt and splash some oil on it. Use Tide-to-Go on half the stain, then wash in the
water basin. Show students that the half which had been treated with Tide washes almost clean, where
the side which was cleansed only with water remains stained.
Question class: How might soap work? Why does it do a better job cleaning than just water? Reserve
judgment on responses.
Show the following YouTube video illustrating how soap works:
http://www.youtube.com/watch?v=ga2ff1nO0uo
Request a summary of the video from students. What two ways does soap work to remove dirt?
Class discussion should be focused on two ways in which soap works to clean:
1. It is a surfactant
What is a “surfactant?” A surfactant reduces the surface tension of water.
How does this help in the removal of dirt? Students will provide a variety of answers. Conversation
should be guided to settle on the fact that the reduction of surface tension allows water to surround
molecules of dirt more effectively, breaking them up.
2. It forms soap micelles around the dirt molecules
What are soap micelles? Soap molecules form “bubbles” around the dirt molecules, allowing water to
wash them away
What property of the molecules in soap (formed during saponification) allows them to form soap
micelles?
They have parts that are hydrophilic (water-loving), and parts that are hydrophobic (water-hating).
Scaffold academic language by asking for a word which may mean water-loving and water-hating (use
“amphibian” as an example). The class should be exposed to the term “amphiphilic”.
In terms of amphiphilicity, how do soap micelles form?
The water-hating (hydrophobic) heads face in toward the dirt molecule. The water-loving tails
(hydrophilic) point out. When the dirt molecule is surrounded, the micelle is washed away by water,
removing the dirt.
Students should remember the concept of amphiphilicity, as it will be important later in the lesson.
Cell membrane discussion (20 minutes)
Show the slide of the cheek cell we have been focusing on over the course of the unit.
Low cognitive demand question: What is the structure around the margin of the cell?
Plasma or cell membrane.
Group Brainstorm (3 minutes)
Why do cells need membranes? What functions does it perform?
If groups have compiled what they feel is a comprehensive list, they may move on to a discussion
focused on creating an analogy for the membrane which fits with our model of the cell as a factory.
A class discussion should ensue, requesting groups share their lists of membrane functions. Important
functions to include are:
1. keep the overall structure of the cell
2. keep things in (i.e. the cytosol)
3. keep things out (i.e. toxins, excess water)
4. movement (show the Amoeba video if necessary: http://www.youtube.com/watch?v=7pR7TNzJ_pA)
So the primary function of the cell membrane is regulate movement of material in and out of the cell.
What kinds of things move across the membrane?
Wastes, nutrients, water, etc.
Can anything move across the membrane?