1. The Cell Membrane
A Web Adventure

2. STRUCTURE AND FUNCTION
The Cell Membrane
STRUCTURE AND FUNCTION

3. The Cell Membrane
Up until now you knew that the function of the cell membrane was to separate the inside of the cell from its outside. In some pictures you have seen, the cell membrane may have looked like this:
Scientists thought that this is what it looked like for a long time.  Then the electron microscope came along and they were able to see the cell membrane.  Below is a picture of how the cell membrane looked to them.  
Use your book and other resources to find out why the cell membrane is so important to all living things.

4. The Cell Membrane
Scientists were then able to break apart the cell membrane and find out what chemicals were in it.  The current best model of what a cell membrane looks like is in the figure below.  As you can see it is made up of two major parts.  

5. Electron Micrograph of the
Plasma Membrane

7. Answer the following questions.
1. Do all living things have cell membranes?
2. What are the primary functions of the cell membrane?
3. Name the 2 major components of the cell membrane.
4. Review the structure of each component by looking in your        book.
5. What is the function of each of these components?
6. What other 2 types of organic molecules are found in the cell membrane? 
7. What roles do they play?  .

8. Construction of the Cell Membrane
Go to this link to build your own cell membrane (Check out the nanotechnology animation!)
Construction of the Cell Membrane
8. How many different types of proteins are components of the cell membrane?
9. What is the function of each type?
10. Explain the role of cholesterol in the cell membrane.
11. Explain why cholesterol is necessary.
12. Explain the relationship between too much cholesterol in your diet and  hardening of the arteries (atherosclerosis).

9. Learn more about the importance of cholesterol in the plasma membrane.
Learn more about the importance of
cholesterol in the plasma membrane.

10. The Cell Membrane
Go to the following web site to learn more details about the structure of the cell membrane.
Cell Membrane - John Kyrk
13. Describe the Davson-Danielli model of the cell membrane and explain why it is no longer accepted. 
14. Explain why the current model of cell membrane structure is called the "fluid mosaic" model. 
Go this site to learn more the structure of the cell membrane  and answer the questions in each quiz.
 Membrane Structure and Function

11. The Cell Membrane
Use your book and other resources to explain the following:
15. Why are so many different types of membrane proteins needed?
16. Explain the difference between integral and peripheral proteins with regard to structure and function. Explain the role that primary structure plays.
17. Is the plasma (cell) membrane homogeneous?
18. What is the function of glycoproteins?
19. What is the function of glycolipids?

12. It is the R groups of the amino acids that determine the location of the protein's side chains in a cell membrane.

13.
The plasma membrane includes three distinct varieties of proteins. Transmembranal (or integral) proteins with hydrophilic ends and hydrophobic midsection, peripheral proteins which are half hydrophilic and half hydrophobic, and surface proteins which are hydrophilic.

15. The Cell Membrane
TRANSPORT

16. Transport
One of the major functions of the plasma membrane is transport. Go to the following web sites to learn more about how molecules, ions, and other materials get into and out of the cell.
Membrane Transport
Membrane Transport tutorial 
Transport In and Out of Cells 
Transport Animation 

17. Transport
1. Why is the movement of materials through the plasma membrane essential for life?
2. What is meant by the term "concentration gradient"?
3. Why is it difficult for a large hydrophilic molecule to pass through a lipid bilayer? What stops it?
4.  Explain the differences between a symport and an antiport.

18. Taking the Easy Way Out (or In)
PASSIVE TRANSPORT
Taking the Easy Way Out (or In)

19. Passive Transport Answer the following questions.
1. Why is the plasma membrane considered to be selectively permeable?
2. Why are membrane proteins considered to be selectively permeable?
3. Name and describe the 3 types of passive transport.
4. You learned that water diffuses through the plasma membrane. Is this what actually happens? Explain how water gets across the membrane. Go to this site to learn more.
My name is Peter Agre.

20. Passive Transport
5. Visit these sites to learn the importance of aquaporins in all organisms. List some of the roles aquaporins play in different types of cells and their role in disease.
 Aquaporin: A Miracle That Can Change the World
Roles of Aquaporins 

21. NOBEL PRIZE IN CHEMISTRY IN 2003
Passive Transport
AQUAPORINS
Click on the link below to see how aquaporins work. You will have to click on the animation to view it.
NOBEL PRIZE IN CHEMISTRY IN 2003

22. Passive Transport - Quick Quiz
Consider the following questions.
1. Which of the following do you think would transport molecules across a membrane faster, a carrier, a channel, or a pump? Explain your reasoning.
2. When would a carrier protein release a bound (hydrophobic) molecule?
3. Why doesn't an aquaporin channel allow a Na+ ion to pass through it?
4. In considering the evolution of wall-less organisms, how might the expression of aquaporins be important?

23. Passive Transport Osmosis - a special type of passive transport
1. What is osmosis and why does it occur?
2. Explain the relationship between osmotic concentration and the following terms:
    a. hypoosmotic / hypotonic
    b. hyperosmotic / hypertonic
    c. isoosmotic / isotonic
3. Which way will water move if the inside of the cell is either a, b, or c in question 2?
Go to this web site to watch an animation and take a short quiz.
How Osmosis Works

25. Passive Transport Osmosis - a special type of passive transport
4.  Define osmotic pressure and explain how it is different from hydrostatic pressure. 
5. Explain what turgor pressure is and its importance to plants.
6. Do animal cells experience turgor pressure? Explain your answer.

26. CONTRACTILE VACUOLES
The Big Squeeze!

27. Contractile Vacuoles The Big Squeeze!
1. Explain how aquatic protists like the Amoeba and Paramecium maintain osmotic equilibrium. Use these sites to help you.
Excretion and Osmoregulation
Osmoregulation in Paramecium
2. Does this involve active or passive transport? Explain your answer.
Watch the video clips on the following slides to see the CV in action.

28. Here is another quick look at what happens.
Look for 2 contractile vacuoles in this critter.

29. Watch the video clip of contractile vacuoles in a Paramecium

30. ACTIVE TRANSPORT
Why is it necessary?

31. Active Transport
1. How does active transport differ from passive transport?
2. Use the sites below to learn more about active transport.
Active Transport
Active Transport tutorial
Cell membrane - Active Transport

32. Active Transport The Sodium-Potassium Pump
This is one of the most important forms of active transport in all organisms. It uses approximately 30% of all the ATP in cells.
Explore the workings of the sodium-potassium pump by viewing some animations and tutorials.
1. Why is the sodium-potassium pump necessary? 
2. What is the ratio of sodium to potassium moving through the membrane?
3. How many ATPs are used per second to keep the pump          
    working?

34. The Sodium-Potassium Pump

35. Active Transport The Sodium-Potassium Pump The Pump Ion Pump
Ion Pump 
Use this site to watch the animation and take a short quiz. 
How the Sodium-Potassium Pump Works
Be sure to read about the Na+ - K+ pump in your book. It outlines the steps very clearly.
4. Explain (in detail) how the sodium potassium pumps works.
5. Name the organs (or tissues) in the human body that would not function without the sodium potassium pump.

36. The Cell Membrane
Take the Challenge!

37. The Cell Membrane A Review
Click on "Lipids and Membranes" in the box on the left and go from there.

38. Take the Challenge! Go to this site and find out how much you know!
Cell Membrane Problem Sets
GOOD LUCK!!!