passive transport
the movement of substances across a cell membrane without the use of energy by the cell
diffusion
movement of molecules from an area of higher concentration to an area of lower concentration.
concentration gradient
the difference in the concentration of molecules across a distance.
equilibrium
the concentration of molecules will be the same throughout the space the molecules occupy.
osmosis
the process by which water molecules diffuse across a cell membrane from an area of higher concentration to a area of lower concentration.
hypotonic
describes a solution whose solute concentration is lower than the solute concentration inside the cell.
hypertonic
describes a solution whose solute concentration is higher than the solute concentration inside the cell.
isotonic
describes a solution whose solute concentration is equal to the solute concentration inside a cell.
cytolysis
the bursting of a cell
facilitated diffusion
the transport of substances through a cell membrane along a concentration gradient with the aid of carrier proteins.
carrier protein (Protein Channel & Pump)
a protein that transports substances across a cell membrane.
active transport
the movement of chemical substances, usually across the cell membrane, against a concentration gradient; requires cells to use energy.
sodium-potassium pump
a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell.
endocytosis
the process by which a cell membrane surrounds a particle and encloses the particle in a vesicle to bring the particle into the cell.
exocytosis
the process by which a substance is released from the cell through a vesicle that transports the substance to the cell surface and then fuses with the membrane to let the substance out.
Homeostasis
The maintenance of a stable internal environment.
Cell membrane
A phospholipid bilayer that regulates the movement of material into or out of the cell.
selectively permeable
some substances can cross the membrane while others cannot