Membrane Transport Mechanisms

Abstract

AS WE SAW IN CHAPTER TWO, A FUNDAMENTAL FEATURE OF MEMBRANES IS a variably-restricted permeability to many of the solutes found in the surrounding aqueous environment. The movement of molecules across membranes may be the result of simple diffusion, or it may involve a complex integration of membrane functions with the energy-yielding metabolic processes of the cell. The molecular nature of both simple and complex transport processes is what concerns us in this chapter. Much of our current knowledge stems from studies on prokaryotes but, as in many other areas of biochemical research, in the absence of evidence to the contrary the molecular mechanisms being elucidated are put forward as models for all biological systems.