transport of a substance (as a protein or drug) across a cell membrane against the concentration gradient
A molecule that has both a hydrophilic region and a hydrophobic region.
A transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane (osmosis).
The process by which large particles and macromolecules are transported through plasma membranes. Inc. exocytosis and endocytosis
proteins carry solutes across cell membrane; specificity: solute binds to a specific receptor site on carrier protein, differs from membrane enzymes because solutes are unchanged; types of carrier mediated transport, facilitated diffusion and active transport
a difference in the concentration of a substance across a distance
The coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient.
the act of dispersing or diffusing something
The diffusion gradient of an ion, representing a type of potential energy that accounts for both the concentration difference of the ion across a membrane and its tendency to move relative to the membrane potential.
An ion transport protein that generates voltage across a membrane.
process by which a cell takes material into the cell by infolding of the cell membrane
the process by which a substance is released from the cell through a vesicle that transports the substance to the cell surface and then fuses with the membrane to let the substance out
movement of specific molecules passively across cell membranes through protein channels
lacking firmness or stiffness
fluid mosaic model
The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids.
A protein channel in a cell membrane that opens or closes in response to a particular stimulus.
A lipid covalently attached to a carbohydrate.
A protein with one or more carbohydrates covalently attached to it.
higher concentration of solute and less free water
lower concentration of solute and more free water
A protein imbedded in the bilayer of the cell membrane
Protein channel in a cell membrane that allows passage of a specific ion down its concentration gradient.
when the concentration of two solutions is the same
of or involving muscular contraction in which tension is constant while length changes
The charge difference between a cell's cytoplasm and the extracellular fluid, due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances.
the control of water balance in a cell
diffusion of molecules through a semipermeable membrane from a place of higher concentration to a place of lower concentration until the concentration on both sides is equal
transport of a substance across a cell membrane, along its concentration gradient, by diffusion without the use of energy
a protein appendage loosely bound to the surface of a membrane and not embedded in the lipid bilayer
process in which phagocytes engulf and digest microorganisms and cellular debris
when a cell is in a hypertonic environment, the cell will lose water to its surroundings, shrink, and its plasma membrane will pull away from the wall
An active transport mechanism in cell membranes that uses ATP to force hydrogen ions out of a cell, generating a membrane potential in the process.
The movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances.
A property of biological membranes that allows some substances to cross more easily than others.
sodium potassium pump
a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell
The ability of a solution to cause a cell within it to gain or lose water.
A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.