Plasma Membrane: Has pores and is selectively permeable to certain molecules and ions.
Solute: Substance that can be
dissolved in a liquid
Solvent: A liquid that dissolves
a solute
Solution: Solute dissolved in
a solvent
Concentration: The amount of material (atoms, molecules, ions, etc.) per unit of volume.
Example - weight of a solute (e.g., kool-aid) in
grams or milligrams per volume (in liters or
milliliters) of water.
150 mg of kool-aid in 100 ml of water
Diffusion: Random movement of
molecules from an area of high concentration to an area of low concentration.
Stops when molecules are uniformly distributed.
Influence of
temperature- As
temperature increases diffusion rate increases & vice versa
gradient- As the gradient increases, diffusion rate increases
molecule size- As
the molecule size decreases, diffusion rate increases
Facilitated diffusion: Diffusion where the solute binds w/a carrier substance to be transported across the semipermeable membrane
Active transport: Process where a cell must expend energy to move molecules across a membrane
Diffusion equilibrium: When influx
and eflux are equal
illustrated examples:
Osmosis: Diffusion of water across a selectively permeable membrane
1. Net
movement of water from an area of high water concentration to an area of
low water concentration
2. Net
movement of water from an area of low solute concentration to an area of
high solute concentration
Isotonic solution: Concentrations
of solutes are the same on both sides of the semipermeable membrane
Hypertonic solution: Higher solute concentration outside of the cell
crenation: shrink
Hypotonic solution: Lower solute concentration outside of the cell
hemolysis: swell
Useful link:
Human Physiology:
Cell Structure & Function