Abstract
Biological membranes consist to a large extent of lipid bilayers, some of which exhibit fairly sharp phase transitions near body temperatures. We describe here a model for the main observed phase transition in pure lipid monolayers and bilayers. The model contains approximate treatments of hard−core repulsions and weak attractive forces between molecules. We believe that the model accounts qualitatively for many of the experimental properties that the model accounts qualitatively for many of the experimental properties of of monolayers and bilayers. Improvements which should enhance quantitative agreement are also discussed.