Cyclodextrins are a group of compounds capable of removing cholesterol from membranes. The effect most likely to have a large impact on cells as a result of cyclodextrin treatment would be

Question

A.  increased concentration of transmembrane proteins.
B.  increased permeability of the membrane.
C.  increased membrane fluidity at lower temperatures.
D.  increased membrane fluidity at higher temperatures.
E.  disruption of transmembrane protein structure.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?

Gather Content
· What do you know about the role of cholesterol in membranes? How does it relate to the question?

Consider Possibilities
· What other information is related to the question? Which information is most useful?

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

D.  increased membrane fluidity at higher temperatures.


Clarify Question
· What is the key concept addressed by the question?
        o The question asks about the role of cholesterol in a membrane.
· What type of thinking is required?
        o You are being asked to apply your knowledge of the role of cholesterol in a membrane to predict what would happen if it were removed.
· What key words does the question contain and what do they mean?
        o Cholesterol in membranes – typically cholesterol increases the fluidity of membranes by preventing the fatty acid tails of phospholipids from clustering together as tightly.

Gather Content
· What do you know about the role of cholesterol in membranes? How does it relate to the question?
        o Biological membranes are typically comprised of mostly phospholipids. Cholesterol in a membrane will prevent the fatty acid tails of the phospholipids from packing together very tightly. This keeps the membrane more fluid.

Consider Possibilities
· What other information is related to the question? Which information is most useful?
        o The drug cyclodextrin removes cholesterol from the membrane. Because cholesterol makes the membrane fluid, removal of cholesterol could make the membrane less fluid.

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o The best answer is that removal of cholesterol would decrease membrane fluidity.
        o Decreased membrane fluidity should not affect the abundance or activity of membrane proteins.
        o Decreased membrane fluidity would also decrease permeability and osmosis rather than increase the activities.

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question asked you to apply your understanding of the role of cholesterol in a membrane to predict what would happen if it was removed. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you recall that cholesterol increases membrane fluidity? Could you predict then that removal of cholesterol would decrease membrane fluidity? Did you understand that decreased fluidity would decrease permeability or osmosis and not increase these activities?