BI110 Chapter 18: Module 18
Document Summary
Diffusion results in the movement of substances down their concentration gradient. Dissolved molecules and ions have thermal energy and therefore are in constant random motion, giving them kinetic energy. Kinetic energy is all the energy required for molecules and ions to spread out from a region of higher concentration to a region of lower concentration. As they diffuse, molecules and ions tend to move down the concentration gradient from a region of high concentration to a region of low concentration. In passive transport, substances exhibit a net movement across plasma membrane due to diffusion. Movement of substance driven by substance"s concentration gradient. Passive transport is responsible for much of the traffic across membrane in/out of cell. A dynamic equilibrium is reached when individual molecules or ions continue to move randomly across the membrane in both directions, but total concentration on both sides does not change; there is no net movement cross membrane.
