BIOLOGY 172 Chapter Notes - Chapter Ch. 41: Distal Convoluted Tubule, Extracellular Fluid, Posterior Pituitary
Document Summary
Homeostasis of water and electrolyte concentration is critical to normal physiological function in all organisms. Osmosis governs the movement of water across cell membranes. Net movement from region of high water concentration to lower water concentration (also from low solute to high solute concentration) Permeable membranes allow water or solutes to diffuse freely. Impermeable membranes block diffusion of water and solutes entirely. Semi-permeable membranes allow movement only of some molecules (i. e. plasma membrane) Aquaporins are channels by which water can move rapidly by facilitated diffusion. Osmosis is the process by which water moves from regions of high water concentration to lower water concentration across a selectively permeable membrane. Net movement of water stops when osmotic pressure equals hydrostatic pressure. Osmotic pressure is the pressure needed to prevent water from moving across a selectively permeable membrane, the tendency of water to move from one solution into another by osmosis. High solute concentration = high osmotic pressure.