PSL201Y1 Chapter Notes - Chapter 1: Retina, Fluid Compartments, Symporter
Document Summary
When oxygen enters a cell/carbon dioxide leaves, molecules move across the plasma membrane spontaneously. + cells don"t need to expend energy to make this happen. + contrast: energy is expended when glucose molecules are transported into epithelial cells in the intestine active transport: transport of molecules across a membrane if it requires energy. Passive transport: does not require energy simple diffusion: movement of a molecule into or out of the cell by its own thermal motion. + one form of passive transport, but certain forms of protein mediated transport are also passive. + contrast: active transport is always mediated by transport proteins (pumps) transport of molecules. + spontaneous (of passive) movement occurs from high energy to low energy; to move in the opposite opposition requires an input of energy. + the energy of a solution depends on the solute concentration (and charge, if the solute is an ion)
