Biochemistry 3380G Lecture Notes - Glycerol, Cytosol, Glycerophospholipid
6 Dec 2012
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Document Summary
Amphipathic lipids have polar groups on one part of the molecule and non-polar ones on the other part and have opposite natures. This results in hydrophilic heads and hydrophobic tails. It is not favourable for the hydrophobic tails to be exposed to water, so they will cluster together to avoid contact. The lipid bi-layer consists of two sheaths or rows of phospholipids with their hydrophobic tails facing each other. The hydrophobic groups are completely shielded by the hydrophilic phosphates. This structural design forms the physical basis of the cell membrane. Lipids move about plane of the lipid bi-layer. Cholesterol, a predominantly hydrophobic molecule, has a different effect on membrane fluidity at different temperatures. At high temperature, lipids are fluid and by filling the membrane with cholesterol, more space is taken up, decreasing fluidity. At low temperatures, a colder membrane is evident and lipids pack together more closely. Thus, cholesterol interferes with this packing, increasing fluidity.
