TBR- Cell Fluidity and Cholesterol- Contradiction?

[AvocadoLover]

Hey all you TBR users! Have any of you noticed a contradiction in the text/psg of Chapter 6? It states in the text "Addition of cholesterol to
a membrane acts to decrease fluidity." Then in Psg X, Question 65 asks "In euk. cells, the plasma membrane consists of relatively large amounts of cholesterol. At such high concentration, cholesterol has the effect of:"
ANSWER- "Increase the fluidity of the membrane by inhibiting hydrocarbon chains from crystallizing."

What's up with that? I did a quick search and found a research article that states "Increasing membrane C/PL (cholesterolhospholipid) causes a decrease in membrane fluidity, and these changes are associated with a reduction in membrane permeability, a distortion of cell contour and filterability and a shortening of the survival of redcells in vivo." So it would seem that the text is right and the psg is wrong. Or am I missing something?

Thanks

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[MegaSpectacular]

Hey all you TBR users! Have any of you noticed a contradiction in the text/psg of Chapter 6? It states in the text "Addition of cholesterol to
a membrane acts to decrease fluidity." Then in Psg X, Question 65 asks "In euk. cells, the plasma membrane consists of relatively large amounts of cholesterol. At such high concentration, cholesterol has the effect of:"
ANSWER- "Increase the fluidity of the membrane by inhibiting hydrocarbon chains from crystallizing."

What's up with that? I did a quick search and found a research article that states "Increasing membrane C/PL (cholesterolhospholipid) causes a decrease in membrane fluidity, and these changes are associated with a reduction in membrane permeability, a distortion of cell contour and filterability and a shortening of the survival of redcells in vivo." So it would seem that the text is right and the psg is wrong. Or am I missing something?

Thanks

cholesterol does both.

It can toughen up the areas around transmembrane proteins, stabilizing the area, hence making it less fluid but also by adding cholesterol you will make it tougher to form a perfect crystal, as you find in your chemistry labs, having 100% of the same molecule forms crystals better than having a few impurities spread out.

Cholesterol does lots of stuff.

Biology is rarely: ____ does _____. It is more like, ____ can do ____ , _____ , _____ and sometimes _____ depending on concentration/environment/conditions/etc.

 

[AvocadoLover]

Thanks so much for your reply Mega! Will keep that in mind!