High-Yield Facts in Physiology GENERAL PRINCIPLES: CELLULAR PHYSIOLOGY (Ganong, pp 1–49. Ryan and Wang, pp 1–2, 7. Widmaier et al., pp 47–61, 107–132, 133–150.) Membrane Transport Mechanisms The transport of ions, gases, nutrients, and waste products through bio- logical membranes is essential for many cellular processes. Diffusion is defined as the net flux of a substance from an area of higher concentration to areas of lower concentration, which does not require energy input...