The Bubbly Structure and Function of Cell Membranes

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Objective

SWBAT compare and contrast the structure and function of a cell membrane with the structure of a bubble.

Big Idea

An engaging lesson that uses a bubble model to explore the structure and function of cell membranes.

Engage

5 minutes

To engage students I begin by showing the attached video (SL.8.5 -Integrate multimedia and visual displays into presentations to clarify information, strengthen claims and evidence, and add interest).

This video does a good job of introducing the relationship between the structure of soap bubbles (i.e. dish detergent) and the structure of cell membranes.  This relationship will be explored in the next part of lesson.

The following are follow up multiple choice questions to the video. Students can write, quiz each other, or vote on the answer (using fingers).

1.  Every cell in your body is separated from the cells around it by its outer most layer called the:

 A Cell bilayer

 B Mitochondria

 C Cell membrane

 D Pseudostratified epithelial

 

2.  What common household product was Agnes Pockles using that started the investigation into the cell membrane?

 A Lysol

 B Dish detergent

 C Baking soda

 D Cane sugar

 

3.  What do we call molecules that have a hydrophilic head and a hydrophobic tail?

 A Mitochondria

 B Proteins

 C Carbohydrates

 D Lipids

 

4.  What were Gorter and Grendel trying to prove?

 A Red blood cells are constructed as a bilayer

 B Every species of animal has a distinct monolayer or bilayer construction of their red blood cells.

 C When a red blood cell bilayer is "unstacked," it yields a monolayer twice its size

 D Both A and C

 

5.  A cell membrane's construction can be likened to a metal jacket. It's strong and sturdy, keeping all the contents of a cell securely in tact.

A True

B False

Teacher Note:  It is good practice to stop video at certain intervals to emphasize key points in video.  Some strategies that can be used are the following:

  • Repeat that last statement (low rigor)

  • Let’s listen again to that last statement (signaling what is important)

    • Structure of lipid (hydrophobic vs hydrophilic)
    • Similarity between structure of bubble and cell membrane'
    • Explanation of how scientists discovered that is was a phospholipid bilayer versus a monolayer
  • How could we put that statement into our own words? (analysis)

Explore

25 minutes

In this part of the lesson students further explore the structure of cell membranes (phospholipids membranes) by studying soap bubbles. Soap bubbles bilayer structure is very similar to that of cell membranes (SP2 - Developing and Using Models - Develop and use a model to describe phenomena).

I have included two resources with this part of the lesson: Cell Membrane Bubble Model Lab and Cell Membrane Soap Bubble Lab Powerpoint.

Cell Membrane Soap Bubble Lab powerpoint is a visual representation of materials and procedure for the lab. It is shown to students as they create their bubble frame.  This powerpoint is a great tool for those students who have difficulty following written directions and require a visual representation of the steps in a procedure. (RST.6-8.3 -Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.) 

Cell Membrane Bubble Model Lab is the actual lab.  The lab document contains a review of cell membrane structure, procedure, and extensions to additional cell biology topics such as transport proteins, cell division, and cell fusion.

Follow up Questions:

I use Fact First Questioning which is a higher-order questioning technique used to draw out student knowledge beyond recall level.  It takes a factual "what" question and turns it into a deeper "how" or "why" question because you are stating a fact first and asking students to elaborate.

1)  The cell membrane is called the Fluid Mosaic Model.  What observations did you make in the lab that can be used as evidence for this claim.

2) A lipid bilayer is a fluid arrangement in which molecules move freely through the plane of the bilayer - reorganizing into almost any shape.  What observations did you make in lab that can be used as evidence for this claim.

3) A cell membrane is not a solid - it is two layers of molecules attracted to each other.  What observations did you make in lab that can be used as evidence for this claim.

Explain

10 minutes

In this part of lesson, students visit cK-12 where they are required to read an article that introduces students to features and roles of cell membrane including its structure and function.  As students read, they complete the questions in Cell Membrane Stop and Jot.  

The objective of this activity is to strengthen students' ability to analyze word meaning from context and introduce students to unfamiliar vocabulary. Further, it solidifies understanding by requiring students to define new vocabulary words as well as generating personal examples of words and concepts. 

Optional: Students may watch video attached to article and answer review questions.

Elaborate

10 minutes

One of the things I strive for is to make sure that students find the relevance to our daily lives as human beings to what they are learning in class.  To accomplish this in this lesson, I have students research one of four cell membrane diseases. I give them a brief description overall, and of each.

Cell membrane diseases are life-threatening disorders that are genetic in nature, and they usually work against proteins in our body that are key to ion channels and various receptors within the membrane. These diseases work by either disrupting the normal functions of the cells or by simply affecting the cell membrane. Many of these disorders contain other components as well.

The students are given the choice to do some research on the following disease which are considered cell membrane diseases:

Hyaline Membrane Disease

  • Commonly associated with preterm infants, Hyaline membrane disease affects the lungs at the time of birth, thus causing respiratory distress. As a result, the lungs require treatment in order to obtain a normal level of oxygen and carbon dioxide exchange.

Alzheimer's Disease

  • The oxidative stress caused by Alzheimer's disease in the brain results in phospholipid altercations. Phospholipids are a key component of our cell membranes. These altercations compromise the cell membrane, therefore disrupting the function of the brain cells.

Cystic Fibrosis

  • Cystic fibrosis is a disease that brings about an excessive production of fluid in the lungs due to a defective calcium-ion channel. This channel contains a protein that is important to the cell membrane of our lungs. The calcium-ion channel controls the level of fluids and mucus in our lungs. When this channel mutates into cystic fibrosis, it causes the mucus to build up in the lungs, thus making it hard to breath.

Duchenne Muscular Dystrophy

  • This disease affects dystrophin in the muscle cell. Dystrophin allows the muscle cell wall to connect with the intracellular section. In the absence of dystrophin, the cell membrane would be incapable of repairing itself, resulting in the destruction of the cell and bringing about Duchenne muscular dystrophy.

In their research, students are required to answer the following questions:

1)  What is the disease?

2)  What are the causes? 

  • How is the function of the cell membrane affected in the disease?

3)  What are thy symptoms? How is the disease diagnosed?

4) What are the treatments?

5) What is the prognosis for someone who is diagnosed with the disease?

This assignment is to be completed at home.

Websites Used 

1. WebMD

2. MayoClinic

3. www.cff.org (Cystic Fibrosis)

4. www.alz.org (Alzheimers)

5. www.mda.org (Muscular Dystrophy)

6. www.childrenshospital.org (Hyaline Membrane Disease)

Evaluate

5 minutes

To evaluate student learning in this lesson, I have them complete a POMS (Point of Most Significance).  

POMS is a metacognitive strategy used to help students connect with important goals of lesson.  Students reflect back on the lesson and identify the key points that contributed to their learning.

I give students the following prompt:

"Today we investigated the structure and function of the cell membrane through various activities; reading of text, video, lab, and discussion.  What point made during today's activities  best helped you understand the structure and function of the cell membrane? Please be specific and describe the activity and its impact on your learning."

I then collect and analyze students' responses to decide if the lesson met its objective or if it needs to be modified.  It's a good idea to let students know that you will use their feedback to seriously consider making changes to your lessons which will benefit them and future students.  Most students will respond to this by responding thoughtfully and with detail.