Cholesterol in membranes confusion

[golgiapparatus88]

In TBR bio, they mention that the more cholesterol a membrane has, the less fluid it will be. To be exact pg 34, "addition of cholesterol to a membrane acts to DECREASE fluidity." So naturally when the question is given "at high concentrations, cholesterol has the effect of...? I first thought that it decreases fluidity. The answer in the back of the book says "at high concentrations, cholesterol acts to INCREASE fluidity."

Are the key words "at high concentration?" Othewise I'm really confused. Hope someone can help.

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[muhali3]

http://forums.studentdoctor.net/showthread.php?t=656922

I think the wording is tricky, but cholesterol prevents the membrane from becoming too fluid or too firm. Its effect on fluidity depends on temperature. Cholesterol does normally have a high concentration in cell membranes, preventing crystallization of the phospholipid fatty acid chains, thus making it more fluid by preventing stiffening.

Anyways I think it's a bad question.

 

[docelh]

Cholesterol has two opposing effects on membrane fluidity. In general, it will impede fluidity if the temperature stays the same. If the temperature falls, it will resist packing and improve fluidity.

 

[TobiasFunkeMDFACS]

For the MCAT, it increases fluidity.

 

[pineappletree]

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What really?

I would think that standard tested scenarios would more accommodate steady temperature, hence Decreasing fluidity...