The movement of any substance across a cell membrane using energy from ATP. The ATP is provided by the cell.
active transport
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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
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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
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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
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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
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The process by which molecules move from an area of greater concentration to an area of lesser concentration.
diffusion
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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
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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
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The biological balance between a cell or organism and its environment. Therefore, it is the balance between everything internal and everything external.
homeostasis
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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
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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
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The engulfing of large food particles by a cell. This is endocytosis of solids.
phagocytosis
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The movement of solutes or fluids into cells. The is endocytosis of liquids or macromolecules.
pinocytosis
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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.