Membrane lipid

The arrangements of lipids and various proteins, acting as receptors and channel pores in the membrane, control the entry and exit of other molecules and ions as part of the cell's metabolism.

Functional roles of lipids are in fact many: They serve as regulatory agents in cell growth and adhesion.

[2] Phospholipids and glycolipids consist of two long, nonpolar (hydrophobic) hydrocarbon chains linked to a hydrophilic head group.

The hydrophobic chains belong either to: Galactolipids – monogalactosyl diglyceride (MGDG) and digalactosyl diglycreride (DGDG) form the predominant lipids in higher plant chloroplast thylakoid membranes; liposomal structures formed by total lipid extract of thylakoid membranes have been found sensitive to sucrose as it turns bilayers into micellar structures.

[4] The fatty acids in phospho- and glycolipids usually contain an even number, typically between 14 and 24, of carbon atoms, with 16- and 18-carbon being the most common.

Plant thylakoid membranes maintain high fluidity, even at relatively cold environmental temperatures, due to the abundance of 18-carbon fatty acyl chains with three double bonds, linolenic acid, as has been revealed by 13-C NMR studies.

Sterols have a hydrophobic four-membered fused ring rigid structure, and a small polar head group.

[6] It associates preferentially with sphingolipids (see diagram) in cholesterol-rich lipid rafts areas of the membranes in eukaryotic cells.