XVI International Botanical Congess

The membranes of plant cells, particularly chloroplast thylakoid membranes, contain molecular species of polar lipids that are highly unsaturated. The fatty acyl constituents tend to be dominated by linolenic acid. Considerable metabolic energy is expended in inserting the double bonds and preserving them in the face of free radical oxidation. The function of these highly unsaturated lipids appears to be more than simply maintaining the membrane in a fluid state over a wide range of environmental temperatures. Studies of the phase behavior of these lipids has led to the idea that unsaturation is an important factor in mediating the interaction of the lipids with intrinsic membrane proteins. Such interactions ensure that the protein distribution and oligmerisation are optimized for the conduct of multicomponent reaction processes. Morever, the interface between protein and lipid becomes effectively sealed against the passage of solutes and ion and other gradients are preserved.