Cholesterol

Functions of Cholesterol:

• reduces permeability to water, ions, and polar molecules
• controls fluidity by preventing phospholipids solidifying at low temperatures and becoming too fluid at high temperatures
• stabilises the phospholipid bilayer by binding polar heads and non-polar tails of phospholipids
• can dissolve into cell membranes- It sits inside cell membranes and in the skin to reduce fluidity

Structure of Cholesterol:

• Lipid
• the -OH group makes it polar at one end
• The four hydrocarbon rings and the hydrocarbon tail are non-polar
• Arranged in bilayers
• All steroids, such as testosterone and progesterone have the 4 ring structure- made from cholesterol 
• cyclic structure with branches- with rings of carbon atoms

Created by the liver- involved in heart disease and gallstones