diffusion- the tendency of molecules to move from an area of higher concentration to an area of lower concentration
concentration gradient- diff in conc. between 2 regions
osmosis- the movement of water molecules through a membrane from a region of higher to a region of lower concentration
solute- substance being dissolved in a liquid (ex. salt)
solvent- substance doing the dissolving (ex. water)
Living things do not require energy to carry on diffusion or osmosis. These processes go down the energy hill.
permeability- the extent to which a membrane will allow particular sized molecules to pass
semi permeable membrane (selectively, differentially permeable)--allows some molecules to pass but not others
(Types of transport in Cells)
1. Passive transport-- movement of substances through a membrane from a region of high to a region of low concentration -- no energy needed (ATP) -- diffusion and osmosis are examples of this
2. Active transport-- movement of substances through a membrane from a region of low concentration to a region of high concentration -- requires cellular energy (ATP)
Two Types of Active transport:
(a.) phagocytosis- cytoplasm of cell surrounds and engulfs particle--ex. ameba and white blood cell
pseudopodia = the engulfing arms of cytoplasm
(b.) pinocytosis- plasma membrane "pinches in" to permit entry of molecules too large to diffuse through the cell membrane