Cholesterol increases membrane fluidity

[aychamo]

Hello there;

In class we learn that "cholesterol increases membrane fluidity at low temperatures, and decreases membrane fluidity at high temperatures." I can see how it would increase fluidity at low temperatures since it attachs to the lipid tails of the membrane, which would push them further apart, making them more fluid. But I can't see how it would decrease fluidity at high temperatures. The only thing I could rationalize is that cholesterol must absorb heat which would make the membrane components less energetic (less moving = less fluidity).

Does that sound about right?

Thank you

 

[Monique]

It was discussed before here https://www.physicsforums.com/showthread.php?t=65214

Cholesterol has a very small head group and a bulky tail group with a rigid steroid ring structure, which cause it to be bend. This bending immobilizes surrounding phospholipids, thus making the membrane less fluid.

and

That is because for a phase transition to occur from a liquid state to a rigid crystalline (gel) state, the hydrocarbon tails need to be closely packed and ordered.

1) cholesterol prevents interaction between hydrocarbon tails of lipids
2) cholesterol is bend and thus prevents close packing

So the membrane remains fluid at lower temperatures, than would normally be allowed.

 

[aychamo]

Ahh, understood. Thank you!

 

[madyus]

Cholesterol is a waxy, fat-like substance that occurs naturally in all parts of the body. Your body needs some cholesterol to work properly. But if you have too much in your blood, it can stick to the walls of your arteries. This is called plaque. Plaque can narrow your arteries or even block them.

High levels of cholesterol in the blood can increase your risk of heart disease. Your cholesterol levels tend to rise as you get older. There are usually no signs or symptoms that you have high blood cholesterol, but it can be detected with a blood test. You are likely to have high cholesterol if members of your family have it, if you are overweight or if you eat a lot of fatty foods.

You can lower your cholesterol by exercising more and eating more fruits and vegetables. You also may need to take medicine to lower your cholesterol.

 

[Cholesterol D]

hi! thanks a lot for your responses. I gained new insight about cholesterol. I was wondering if you can also post examples of your researches or investigatory projects regarding cholesterol? i badly need one for school and I don't know where to start.

http://www.all-about-lowering-cholesterol.com/diet-for-lowering-cholesterol.html"