Chapter 3

Passive Transport  Diffusion – molecules move spontaneously (no energy used) from an area of high concentration to an area of low concentration.  Facilitated diffusion – molecules diffuse through a membrane by means of a carrier molecule. (no energy)

Passive Transport  Osmosis – the diffusion of water through a selectively permeable membrane  Osmotic pressure = pressure to stop osmosis  Filtration – molecules are forced through a membrane by hydrostatic pressure

Active Transport  Molecules are moved against the concentration gradient.  Requires the use of cellular energy  Exocytosis – transport of particles out of the cell  Endocytosis – transport of particle into the cell  Pinocytosis – liquids taken in  Phagocytosis – solids taken in

Solutions  Solute – Substance dissolved  Solvent – Substance in which a solute is dissolved (usually water)  Ex. Sugar (solute) dissolved in water (solvent)

Solutions  Hypertonic Solution – concentration of solute particles is greater outside the cell  Causes water to go out of cell

Solutions  Hypotonic Solution – concentration of solute particles is lower outside the cell  Causes water to enter the cell

Solutions  Isotonic Solution – concentration of solute particles is the same inside and outside  Cause water movement to be equal