concept 7.3: passive transport is diffusion of a substance across a membrane with no energy investment

diffusion

movement of particles of any substance so that they spread out evenly into the available space

what happens at dynamic equilibrium

as many molecules cross the membrane in one direction as in the other (no net movement)

in what direction do substances diffuse

down their concentration gradient from high to low concentration

what does the concentration gradient represent

potential energy that drives diffusion

describe the diffusion of a substance across a biological membrane

passive transport, spontaneous, exergonic, -delta G

simple diffusion

the movement of gases (O2 and CO2) and lipids through the phosopholipid bilayer

facilitated diffusion

transport proteins speed the passive movement of molecules across the plasma membrane

what are transport proteins

channel proteins and carrier proteins

cystinuria

a disease causes by the malfunctions in specific transport system, cysteine is not transported back into kidney calls