BIOL 2160 Chapter : Test 2 Chapter 4
Document Summary
Small or nonpolar molecules can freely diffuse across the membrane. Large or polar molecules need carrier proteins to move across membrane. Passive transport-transport across the membrane does not require energy. Active transport-transport across the membrane requires energy (pump) All has to do with if its going down concentration gradient or up concentration gradient. Molecules move across membranes from high energy to low energy. Energy of a solution depends on solute concentration. Therefore, solutes move passively from areas of high concentration to areas of low concentration. K is 30:1, huge concentration gradient wanting to push k out of cell. Sodium is 10:1, still pretty big gradient wanting to push sodium into cell. Always way more k inside, and way more na outside. Charged molecules can"t cross without help of other proteins- no simple diffusion, so ion concentrations don"t eventually even out.
