Cell Function Flashcards
Diffusion
Movement of ANY molecules from a region of high to low concentration of that substance (along a concentration gradient), until equilibrium is reached
Osmosis
Movement of water molecules from a region of high water to low water concentration through a selectively permeable membrane.
Facilitated Diffusion
Molecules move along a concentration gradient, but this movement is assisted by carrier proteins in the membrane.
Each protein that acts as a membrane-transporter is specific to one solute or several similar solutes and allows the movement of a large or charged molecule.
The protein may act in one of two ways— as a channel protein or a carrier protein.
Active Transport
Movement of molecules from a low concentration to a high concentration through selectively permeable membrane
Isotonic
Fluids inside and outside a cell are of equal solute concentration – no net water movement.
Hypertonic
A solution of higher solute concentration (lower water concentration) that surrounds a cell – net movement of water molecules will be out of the cell.
Hypotonic
A solution of lower solute concentration (higher water concentration) that surrounds a cell – net movement of water molecules will be into the cell.
Endocytosis
Endocytosis moves large molecules that cannot cross the cell membrane into a cell. It requires the expenditure of energy.
The cell membrane changes shape and surrounds and engulfs the particle so that it enters the cell.
Phagocytosis
The process whereby solid particles are engulfed by the cell membrane.
Pinocytosis
The engulfing of fluid substances by the cell membrane.
Exocytosis
Exocytosis involves a membrane-bound vesicle moving to the cell membrane, fusing with it and then releasing its contents to the exterior of the cell.
Surface Area : Volume Ratio
The surface-area-to-volume ratio (SA:V) of a cell will determine how efficiently substances move into and out of a cell.
A high SA:V allows the most efficient movement of substances into and out of the cell.
Large cells have a low SA:V. Small cells have a large SA:V.
Long, flat cells have a higher SA:V than spherical cells with the same volume.
