The movement of a substance across a biological membrane against its concentration or electrochemical 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 a membrane
An increase or decrease in the density of a chemical substance in an area
The coupling of the "downhill" diffusion of one substance with the "uphill" transport against its own concentration gradient
the process by which molecules move from an area of higher concentration to an area of lower concentration
The diffusion gradient of an ion, which is affected by both the concentration difference of the ion across a membrane (a chemical force) and the ion's tendency to move relative to the membrane potential (an electrical force).
An active transport protein that generates voltage across a membrane while pumping ions.
the process by which a cell membrane surrounds a particle and encloses the particle in a vesicle to bring the particle into the cell
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
the transport of substances through a cell membrane along a concentration gradient with the aid of carrier proteins
Limp. Lacking in stiffness or firmness, as in a plant cell in surroundings where there is no tendency for water to enter the cell.
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.
lipid substances with linked sugar groups that are key structural elements in cell membranes and precursors of other biologically active molecules important in cell signaling
Proteins that have carbohydrates covalently bonded to them.
when comparing two solutions, the solution with the greater concentration of solutes
when comparing two solutions, the solution with the lesser concentration of solutes
extend entirley through the membrane with both hydrophobic and hydrophilic ends (imbedded)
a transmembrane protein channel that allows a specific ion to flow across the membrane down its concentration gradient
having a solute concentration equal to that of another solution
A molecule that binds specifically to a receptor site of another molecule.
The charge difference between a cell's cytoplasm and the extracellular fluid, due to the differential distribution of ions.
The control of water balance in organisms living in hypertonic, hypotonic, or terrestrial environments.
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
The movement of substances across a cell membrane without the use of energy by the cell.
Protein appendages loosely bound to the surface of the membrane and not embedded in the lipid bilayer.
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 consumes ATP to force hydrogen ions out of a cell and, in the process, generates a membrane potential
A property of biological membranes that allows some substances to cross more easily than others.
A special transport protein in the plasma membrane of animal cells that transports sodium out of the cell and potassium into the cell against their concentration gradients.
The ability of a solution to cause a cell within it to gain or lose water.
protein molecules that help to transport substances throughout the body and across cell membranes
Firm. Walled cells become turgid as a result of the entry of water from a hypotonic environment.