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| a property of biological membranes that allows some substances to cross more easily than others and blocks the passage of other substances altogether. |
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| a description of membrane structure, depicting a cellular membrane as a mosaic of diverse protein molecules embedded in a fluid bilayer made of phospholipid molecules. |
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| on or in a cell, a specific protein molecule whose shape fits that of a specific molecular messenger, such as a hormone. |
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in cell biology, a series of molecular changes that converts a signal on a target cell's surface to a specific response inside the cell. |
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| the spontaneous movement of particles of any kind from where they are more concentrated to where they are less concentrated. |
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| an increase or decrease in the density of a chemical substance in an area. Cells often maintain concentration gradients of ions across their membranes. |
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| the diffusion of a substance across a biological membrane, without any input of energy. |
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| the passage of a substance across a biological membrande down its concentration gradient, aided by specific transport proteins. |
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| the diffusion of water across a selectively permeable membrane. |
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| the ability of a solution to cause a cell within it to gain or lose water. |
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| a solution having the same solute concentration as another solution. |
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in comparing two solutions, the one with the lower concentration of solutes. |
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| in comparing two solutions, the one with the greater concentration of solutes. |
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| the control of the gain and loss of water and dissolved solutes in an organism. |
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| a phenomenon that occurs in plants in an hypertonic solution. The cell loses water and shrivels, and its plasma membrane pulls away from the cell wall, usually killing the cell. |
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| the movement of a substance across a biological membrane against its concentration gradient, aided by specific tranport proteins and requiring input of energy (often as ATP). |
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| the movement of materials out of the cytoplasm of a cell via membranous vesicles or vacuoles. |
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| the movement of materials into the cytoplasm of a cell via membranous vesicles or vacuoles. |
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| cellular "eating'; a type of endocytosis whereby a cell engulfs macromolecules, other cells, or particles into its cytoplasm. |
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| an inherited human disease characterized by an excessively high level of cholesterol in the blood. |
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