Welcome back to my channel, in today’s video, we are going to look at the structure of cholesterol and the function of cholesterol in the cell membrane. Cholesterol is found throughout animal cell membranes. It is not present in the cell membranes of plant cells as they have a cellulose cell wall that helps to support the cell membrane. Cholesterol is a lipid that is identifiable by its four-wing structure. It consists of four linked hydrocarbon rings, forming the steroid portion of the molecule. Extending from one end of this steroid is a hydrocarbon chain. Extending from the other end is a hydroxyl group. Cholesterol is amphipathic, which means part of it is hydrophilic and other parts are hydrophobic. The steroid portion and hydrocarbon tail are hydrophobic. Whilst the hydroxyl group is hydrophilic. Within the phospholipid bilayer, the cholesterol sits in this membrane with the hydroxyl group which is polar and hydrophilic in with the polar and hydrophilic phospholipid heads The hydrophobic steroid rings and hydrocarbon chain portions of the cholesterol molecule are found embedded in the hydrophobic portion of the membrane with the phospholipid fatty acid tails. These cholesterol molecules carry out an important function in the cell membrane. They function in both regulating the fluidity of the cell membrane as well as regulating the permeability of the cell membrane. The location of cholesterol between phospholipids helps stabilize the membrane, giving it additional support in the absence of a cell wall. This stabilization allows the cell membrane to remain fluid but reduces the fluidity overall of the cell membrane. In addition, the presence of cholesterol between the phospholipids prevents the phospholipids from coming into contact which prevents them from stiffening or crystallizing. Cholesterol’s presence in the cell membrane is also in regulating the permeability of the cell. If the cell membrane is too fluid, the permeability of it would be too much which would allow too many molecules to pass into the cell. If it was too stiff and had too little fluidity, not enough molecules would be able to pass through into the cell. Thank you for watching, to support this channel please subscribe and check out more of my videos.