Membrane fluidity...

[jsong812]

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I was doing a couple of problems from the EK 1001 biology book today and I happened to come across a problem which had a solution that I didn't agree with. Moreover, it involved regulating membrane fluidity. From what I remember in my cellular biology class ( I could be wrong), shouldn't an increase in cholesterol concentration stiffen the membrane? The EK book says otherwise- "higher organisms... increase membrane fluidity by increasing the concentration of cholesterol." For those of you who have the book are interested in which problem I am referring to, it is number 236 in lecture 3. thanks!

-james

 

[ulalalalaboy]

EK is right. I took bio and the book says the same thing as EK.

 

[Kristiyana]

For the purpose of the MCAT, EK is correct ... I believe it's a bit more complex than that (i.e., dependent on temperature etc.,), but that's not important here ...

 

[Sol Rosenberg]

I was doing a couple of problems from the EK 1001 biology book today and I happened to come across a problem which had a solution that I didn't agree with. Moreover, it involved regulating membrane fluidity. From what I remember in my cellular biology class ( I could be wrong), shouldn't an increase in cholesterol concentration stiffen the membrane? The EK book says otherwise- "higher organisms... increase membrane fluidity by increasing the concentration of cholesterol." For those of you who have the book are interested in which problem I am referring to, it is number 236 in lecture 3. thanks!

-james

Cholesterol increases membrane fluidity at lower temperatures (prevents packing of phospholipids into a solid) but decreases membrane fluidity at higher temperatures. Summing it up -- Cholesterol moderates membrane fluidity in ANIMALS (I got a test question wrong in "Bio 101" where I picked an answer that had plants having cholesterol in their membranes, which they DON'T.) But since the MCAT is pretty much animals only, forget what I just said about plants.

Jota

 

[jsong812]

Cholesterol increases membrane fluidity at lower temperatures (prevents packing of phospholipids into a solid) but decreases membrane fluidity at higher temperatures. Summing it up -- Cholesterol moderates membrane fluidity in ANIMALS (I got a test question wrong in "Bio 101" where I picked an answer that had plants having cholesterol in their membranes, which they DON'T.) But since the MCAT is pretty much animals only, forget what I just said about plants.

Jota

aah... "regulating;" that makes much more sense now. Thanks jota.