Cell membrane and Transport

Presented by Belghith Abidi

Introduction of the cell membrane

• Humans consume food every day and produce metabolic wastes. How do cells absorb the nutrients and get rid of the wastes?

• The cell membrane which is the gate to the cell offers us the answer to this question

Outline of lesson sequence

Lesson 1: Revision of Basic biochemistry and introduction to the unit of cell membrane and transport

Lesson 2: General structure of the cell membrane Lesson 3: Proteins, polysaccharides, and cholesterol in the cell

membrane Lesson 4: The process of osmosis Lesson 5: Diffusion and facilitated diffusion Lesson 6: Lab on osmosis in red onion cells Lesson 7: Active transport mechanism Lesson 8: Lab on the effect of temperature on the diffusion of

pigments in root beet Lesson 9: Overall revision and Gizmos activity

Curriculum expectations

A1. Scientific investigation skills Initiating and Planning [IP]*

A1.1 , A1.2 , A1.4 Performing and Recording [PR]*

A1.5 , A1.6 Analyzing and Interpreting [AI]*

A1.8 , A1.10 Communicating [C]*

A1.11

A2. Career Exploration A2.1 B1. Relating Science to Technology, Society, and the Environment B1.2 B2.Developing Skills of Investigation and Communication B2.1, B2.2 B3. Understanding Basic Concepts B3.1

PART 1:Overview of the structure

of the cell membrane

Overview of the structure of the cell membrane

Introduce the main function of the cell membrane using a video and diagramshttps://www.khanacademy.org/test-prep/mcat/cells/cell-membrane-overview/v/cell-membrane-introduction

Worksheet : labeling a diagram of the cell membrane (worksheet) Explain the structure and function of each component one by one including

phospholipids, proteins, cholesterol and polysaccharides

-Watch a video on phospholipids:https://www.khanacademy.org/test-prep/mcat/cells/cell-membrane-overview/v/phospholipid-structure

-Present a diagram showing the structure of phospholipid molecules with their polar hydrophilic heads and non polar hydrophobic tails

Phosphate group head Hydrophilic

Fatty acid tails hydrophobicArranged as a bilayer

-Watch a video on phospholipids:https://www.khanacademy.org/test-prep/mcat/cells/cell-membrane-overview/v/phospholipid-structure

Present a diagram showing the structure of phospholipid molecules with their polar hydrophilic heads and non polar hydrophobic tails

polarhydrophilic

heads

polarhydrophilic

heads

Non polarhydrophobic

tails

Discussing the phospholipid bilayer using a diagram

Discussing the role of cholesterol as a buffer that maintains membrane fluidity

(explicit teaching)

Non polar moleculesEmbedded inside the membraneRegulate fluidity of cell membrane

• Show a video on cell membrane proteinshttps://www.khanacademy.org/test-prep/mcat/cells/cell-membrane-overview/v/cell-membrane-proteins

• Differentiate between the different types of proteins (integral and peripheral)

Carbohydrates: Types and Roles

Present a diagram of carbohydrates and discuss the different types (glycoprotein and glycolipids) and their role in:• Cell-cell recognition: ability of a cell to distinguish one cell from

another• As antigens: important in organ & tissue development basis for

rejection of foreign cells

PART 2:OVERVIEW OF THE CELL MEMBRANE

FUNCTIONS

TRANSPORTS ACROSS THE CELL MEMBRANE

Differentiate between Active and Passive transport mechanism and list the different types

Osmosis

Diffusion

Facilitated diffusion

Sodium potassium pump

Endocytosis

Exocytosis

Watch a video on how osmosis works as a preparation for the lab activity

http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

Lab activity on the process of osmosis in red onion cells. Students will submit a lab report

Exploring Osmosis

Exploring Diffusion

Class demonstration of osmosis and diffusion using dialysis bag followed by discussion questions to consolidate the concepts of diffusion and osmosis

the diffusion of iodine and water into in dialysis bag containing starch turns the starch suspension turns blue and the increase in the volume of the dialysis bag proves the process of osmosis)

Inquiry question: How does this experiment demonstrate selective permeability?

Myth about Osmosis and Diffusion

Fact: Students often confuse he concepts of hypotonic and hypertonic and its relation with osmosis. They think that water diffuses from hypertonic to hypotonic, considering water as a solute.

Consolidating activity: In 3 beakers A, B, and C put 100 ml of 5% sucrose solution. Pour 10 ml of a 1% sucrose in a dialysis bag A and place it in beaker A, 10 ml of a 5% sucrose in a second dialysis bag B and place it in beaker B, and 10 ml a 15% sucrose in a third dialysis bag C and place it in beaker C. Wait 15 minutes and then measure the final volume in the 3 different bags by emptying the volume of each bag in a graduated cylinder.

Exploring Facilitated Diffusion

Watch a video about how facilitated diffusion works http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html

Using diagrams discuss the role of carriers and protein channels involved in facilitated diffusion

Group work: answering a worksheet related to proteins involved in passive transport

Lab activity: effect of temperature on the cell membrane permeability

Exploring the effect of temperature on the movement of anthocyanin, a red pigment in the vacuole of beetroot cells, through the cell membrane.In this experiment, students use the colorimeter to measure the level of pigmentation in the soaking solution at different temperatures

Explore the active transport

Na/K pumpWatch a short video :https://www.youtube.com/watch?v=P-imDC1txWw

Compare the Na/K pump to facilitated diffusion

Group work: Data analysis question on the effect of inhibiting ATP production on the active transport mechanism

Exploring the active transport

EndocytosisWatch a short video on endocytosis http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__phagocytosis.html

Answer the self assessment questions that follow

Discuss the answers and provide feedback

Using a diagram, discuss the process of exocytosis

Exocytosis

For revision, students could use the following site https://www.youtube.com/watch?v=qasm7Mj7CYg endocytosis and exocytosis by Khanacademymedicine

Gizmos activity: homeostasis in Paramecium

Group work: Gizmos activity related to homeostasis in Paramecium solve in group the self- assessment questions that followhttp://www.explorelearning.com/index.cfm?method=cResource.dspView&ResourceID=520

Application to everyday life

Watch the video on hemodialysis: https://www.youtube.com/watch?v=8YmJUpb8G74The semipermeable nature of the cell membrane is used to design the artificial dialysis device or artificial kidney. Compare hemodialysis to the transport mechanism in cells in terms of selective permeability and active and passive transport mechanism Discuss the societal implication of hemodialysis or peritoneal dialysis on patients suffering from kidney disorder

SOMES DIFFICULTIES

In concepts:How to distinguish between facilitated diffusion and diffusion1. How to distinguish between

facilitated diffusion and active transport through carrier molecules and protein channels

2. The concepts of hypotonic and hypertonic and its relation with osmosis (they tend to think that water diffuses from hypertonic to hypotonic, considering water as a solute)

In lab sessions:• The proper use of the

colorimeter• The proper use of the

microscope • The proper timing for the

observation of the plasmolyzed cells before they deplasmolyze

References & Resources

"Animation: How Osmosis Works." Animation: How Osmosis Works. Date accessed: 22 July 2015http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html "Animation: Phagocytosis." Animation: Phagocytosis. Date accessed: 22 July 2015. http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__phagocytosis.html "Artificial Kidneys - Dialysis Machine....." YouTube. YouTube. Date accessed: 22 July 2015.https://www.youtube.com/watch?v=8YmJUpb8G74 "Cell Membrane Introduction." Khan Academy. Date accessed: 22 July 2015https://www.khanacademy.org/test-prep/mcat/cells/cell-membrane-overview/v/cell-membrane-introduction  "Endocytosis Exocytosis." YouTube. YouTube. Date accessed. 22 July 2015https://www.youtube.com/watch?v=qpw2p1x9Cic "Fluid Mosaic Model." YouTube. YouTube. Date accessed: 22 July 2015.https://www.youtube.com/watch?v=Qqsf_UJcfBc "How Facilitated Diffusion Works [HD Animation]." YouTube. YouTube. Date accessed: 22 July 2015.https://www.youtube.com/watch?v=mzo_B5F7pk4 "How the Sodium Potassium Pump Works." YouTube. YouTube. Date accessed: 22 July 2015.https://www.youtube.com/watch?v=P-imDC1txWw Homeostasis in Paramecium”.Gizmos. Date accessed: 22 July 2015http://www.explorelearning.com/index.cfm?method=cResource.dspView&ResourceID=520 "Membrane Transport in Cells: Symport, Antiport, Co-transport [3D Animation]." YouTube. YouTube. Date accessed: 22 July 2015.https://www.youtube.com/watch?v=svAAiKsJa-Y