The Cell Membrane
A Web Adventure
The Cell Membrane
STRUCTURE AND FUNCTION
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.
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.
http://cellbiology.med.unsw.edu.au/units/science/lecture0803.htm
Electron Micrograph of the
Plasma Membrane
http://www.hillstrath.on.ca/moffatt/bio3a/cellbio/phase1.htm
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?
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).
http://academic.brooklyn.cuny.edu/biology/bio4fv/
page/lipids-cholesterol.html
http://www.erin.utoronto.ca/~w3bio315/lecture2.htm#section7
Learn more about the importance of
cholesterol in the plasma membrane.
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
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?
It is the R groups of the amino acids that determine the
location of the protein's side chains in a cell membrane.
http://www.new-science-press.com/browse/protein/illustrations/ud/
http://home.earthlink.net/~dayvdanls/cell_membranes.htm
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.
The Cell Membrane
TRANSPORT
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
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.
PASSIVE TRANSPORT
Taking the Easy Way Out (or In)
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.
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
http://virtuallaboratory.colorado.edu/Biofundamentals/lectureNotes/Topic2E_Membranes.htm
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
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?
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
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.
CONTRACTILE VACUOLES
The Big Squeeze!
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.
Here is another quick look at what happens.
Look for 2 contractile vacuoles in this critter.
Watch the video clip of contractile
vacuoles in a Paramecium
ACTIVE TRANSPORT
Why is it necessary?
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
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?
The Sodium-Potassium Pump
Active Transport
The Sodium-Potassium Pump
The 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.
The Cell Membrane
Take the Challenge!
The Cell Membrane
A Review
Click on "Lipids and
Membranes" in the box on the
left and go from there.
Take the Challenge!
Go to this site and find out how much you know!
Cell Membrane Problem Sets
GOOD LUCK!!!