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15 Cards in this Set

  • Front
  • Back
selective permeability
membrane is a barrier allowing some substances to pass through more readily than others
lipid bilayer permeability
permeable to nonn-polar uncharged molecules (0,C02, steroids)
slightly permeable to H2O & urea (leak through as lipids flip-flop)
channels & transporters provide selective permeability
2 criterion used to classify transport processes
1) mediation
2) Energy used (active/passive)
mediated transport
involves assistance of a transporter protein
non-mediated transport
does not require a transporter protein
(lipid layer/channel diffusion)
Active transport
needs additional energy (usually ATP) to move up a concentration gradient
Passive transport
uses chemical's kinetic energy to move down a concentration gradient
concentration gradient
the difference in the concentration of a chemical from one place or another
electrical gradient
the difference in electrical charges in two regions;
it occurs across the plasma membrane so it is termed
electrochemical gradient
combined influence of concentation gradient and membrane potential
(in a solution)
passive process
random mixing of particles in a solution
solute moves down it's concentration gradient in the solvent
until equilibrium is reached
dissolved substance
liquid that does the dissolving
particles are evenly distributed in the solution
Laws of Diffusion

(factors that influence diffusion across a membrane)
1) steepness of concentration gradient
2) temperature
3) mass of the diffusing substance
4) surface area
5) diffusion distance