Pumping of a specific solute across a cell membrane against its concentration gradient, through the interior of a transport protein. Requires energy input, as from ATP.
Of multicelled species, a plasma membrane protein that helps cells stick together in tissues and to extracellular matrixes such as basement membrane.
Large microbial populations that anchored themselves to epithelium, rocks, or other surfaces by their own secretions.
The mass movement of one or more substances in the same direction, most often in response to pressure.
Active transport protein; pumps calcium ions across a cell membrane against their concentration gradient.
A membrane protein that helps form an open channel between the cytoplasm of adjoining cells.
Difference in the number of molecules or ions of any one substance between two adjoining regions.
Net movement of like ions or molecules from a region where they are most concentrated to an adjoining region where they are less concentrated; they move down their concentration gradient.
A difference in electric charge between adjoining regions.
Cell uptake of substances by forming vesicles from patches of plasma membrane. Three modes are receptor-mediated endocytosis, phagocytosis, and the bulk transport of extracellular fluid.
Fusion of a cytoplasmic vesicle with the plasma membrane; as it becomes part of the membrane, its contents are released to extracellular fluid.
fluid mosaic model
A cell membrane has a mixed composition (mosaic) of lipids and proteins, the interactions and motions of which impart fluidity to it.
Pressure exerted by a volume of fluid against a cell wall, membrane, or some other structure that contains it; also called turgor pressure.
Of two fluids, the one with the higher solute concentration.
Of two fluids, the one with the lower solute concentration.
Any fluid having the same solute concentration as another fluid to which it is being compared.
Structural basis of all cell membranes; mainly phospholipids arranged tail-to-tail in two layers, with hydrophilic heads of one dissolved in cytoplasmic fluid and heads of the other in extracellular fluid.
Diffusion of water across a selectively permeable membrane from a region where the water concentration is higher to a region where it is lower.
The amount of pressure which, when applied to a hypertonic fluid, will stop osmosis from occurring across a semipermeable membrane.
Diffusion of a solute across a cell membrane, through the interior of a transport protein.
[Gk. phagein, to eat] �Cell eating,� a common endocytic pathway by which various cells engulf food bits, microbes, and cellular debris.
A lipid with a phosphate group in its hydrophilic head. The main constituent of cell membranes.
Difference in pressure between two adjoining regions.
One of a class of glycoproteins or glycolipids that project above the plasma membrane and that identify a cell as nonself (foreign) or self (belonging to one�s own body tissue).
Built-in capacity of a cell membrane to prevent or allow specific substances from crossing it at certain times, in certain amounts.
Cotransporter that, when energized, actively transports sodium out of a cell and helps potassium passively diffuse into it at the same time.
Relative solute concentrations of two fluids.
Membrane protein that passively or actively assists specific ions or molecules into or out of a cell. The solutes move through the protein�s interior.