BI110 Chapter Notes - Chapter 18: Facilitated Diffusion, Passive Transport, Semipermeable Membrane
Document Summary
Hydrophobic nature of membranes restricts free movement of many molecules and substances essential for life. Passive transport: movement of a substance across a membrane without need to expend chemical energy such as atp. Passive transport can be driven by diffusion. Diffusion: net movement of a substance from region of higher to lower concentration. Primary mechanism of solute movement within a cell and between cellular compartments separated by a membrane. Rate of diffusion depends on the concentration difference on two sides of membrane, or the concentration, more potential gradient. The concentration gradient is a form of potential energy (not atp) so the bigger the concentration gradient, the faster the rate of diffusion (more concentration, more potential energy) Molecules that are dissolved move around (kinetic energy), which is the concentration gradient is a form of potential energy. Diffusion rates are also affected by temperature and molecule size. As the temperature increases, rate of diffusion increases.