Re: how can temperature affect the cell membrane and its permeability?

	The cell membrane is not a homogenous mixture of molecules.  It is 
composed of proteins, lipids, and carbohydrates.  All of these molecules are 
affected by temperature changes.  The membrane's Tm (melting point) is 
affected by the composition of the membrane.  Membrane permeability is a 
function of this composition and of transporters present in the membrane.  
You may find the following review helpful: "Morphological, physiological and 
biochemical parameters associated with cell injury: a review." 
Immunopharmacol Immunotoxicol 1989;11(4):539-58.  If you do not have access 
to this journal, your library can order a copy of the paper through the 
National Library of Medicine, Bethesda MD 20892.
	An exciting new field of biology is the study of specific groups of 
molecules present in the membrane.  It has been discovered that certain 
components of the membrane aggregate (clump) together.  These aggregates are 
called rafts and may be important in cell signalling.  There is at least one 
excellent review of this area in the 1998 journal Annual Reviews of Cellular 
and Developmental Biology. Thus the membrane may not only govern cellular 
permeability, but may also play a role in cellular signalling.