The movement of any substance across a cell membrane using energy from ATP. The ATP is provided by the cell.
active transport
A protein that functions in the transport of molecules across a membrane. The proteins are embedded in the cell membrane. They bond with the molecule to be carried, transport it to the opposite side of the membrane, and release it.
carrier molecules
The difference in concentration of a substance across a space. This usually starts with a high concentration and flows into a low concentration.
concentration gradient
An organelle in (unicellular) microorganisms that excretes water by forcing it out through the cell membrane. This helps keep the water balance within the cell.
contractile vacuole
The "bursting" of a cell. It occurs when a cell takes in so much water that it bursts. It bursts because of internal pressure.
cytolysis
The process by which molecules move from an area of greater concentration to an area of lesser concentration.
diffusion
The process by which a cell engulfs and surrounds a large substance. The cell membrane forms an involution around the particle. The sides of the involution pinch together to form a vacuole / vesicle inside the cell.
endocytosis
The process by which wastes and other substances are packaged in vacuoles / vesicles and leave the cell. This process uses microvilli and is the opposite of endocytosis.
exocytosis
The biological balance between a cell or organism and its environment. Therefore, it is the balance between everything internal and everything external.
homeostasis
The diffusion of water through a semipermeable membrane, from an area where there is a high concentration of water into an area where there is a lower concentration of water.
osmosis
The movement of any substance across a cell membrane without the use of the cell's energy. The molecules use their own internal kinetic energy to move.
passive transport
The engulfing of large food particles by a cell. This is endocytosis of solids.
phagocytosis
The movement of solutes or fluids into cells. The is endocytosis of liquids or macromolecules.
pinocytosis
Water pressure within a plant cell. It occurs when water enters the cell by osmosis. It is seen in plant cells because of the presence of a cell wall.
turgor pressure
