MEMBRANES
Membranes are mostly 6 to 12 nm thick. Membranes limit close capacities of various shape and size; for example, bubbles, applanate cavities and whole cells. Thus, preventing diffusion, membranes form separate reaction chambers ( compartments). Membranes are selectively permeable for some substances and actively pump others, and this is accompanied by energy input. Membranes are two-dimensional liquid-crystal solution of globular proteins in lipids. Structural basis of membranes is formed by lipids, among which phospholipids are the most abundant. In membranes of organelles glycolipids prevail. Proteins in membranes perform certain functions: they, for example, serve as enzymes or transport proteins. Besides, membranes contain sterols (cholesterol), glycoproteids and some inorganic salts.