5 - Lipid Domains and Biological Membrane Function

Abstract

This chapter discusses the morphometric features of cells as well as the general structure and function of biological membranes. It is mentioned that the major chemical entities responsible for membrane formation are lipids. The clear structure adopted by lipids in biological membranes has evolved into the “fluid mosaic” model wherein a fluid lipid bilayer serves as a matrix for embedded proteins functioning as ion channels, receptor-effector coupled systems, transporters, and others. The general structure of biological membranes include cell surface plasma membrane, intracellular membranes of eukaryotic cells like the endoplasmic reticulum (ER), Golgi complex, lysosome, peroxisome, mitochondria and the nuclear membrane, and the structure of biomembrane lipid bilayer. The chapter also highlights the progress in the existing membrane models postulated by different researchers. The chapter includes the macroscopic and microscopic domains of the transbilayer lipid distribution in plasma membranes. The microscopic domains include phospholipid transbilayer, cholesterol transbilayer, sphingolipid and glycolipid transbilayer, fatty acid transbilayer domains, and regulation and pathophysiology.The section of lateral lipid microdomains in membranes includes plasma membrane lateral microdomains of sphingolipids and glycolipids, cholesterol lateral microdomains in plasma membranes, and regulation and pathophysiology of plasma membrane lateral domains The lipid domain fluidity of lateral plasma membrane includes macroscopic lateral lipid domains, microscopic plasma membrane lateral domains, and the structural consequences of lipid lateral domains in model membranes. The chapter concludes by stating that the molecular biologist must begin identifying specific genetic sequences coding for the proteins that regulate lipid domains in membranes and for proteins that direct lipid trafficking from intracellular sites of synthesis.