Ch. 7 Vocab Flashcards
a region along which the density of a chemical substance increases or decreases
concentration gradient
channel proteins in the plasma membrane of a plant, animal, or microorganism cell that specifically facilitates osmosis; the diffusion of water across the membrane
aquaporins
the movement of a substance across a cell membrane with an expenditure of energy, against its concentration or electrochemical gradient; mediated by specific transport proteins
active transport
having both a hydrophilic region and a hydrophobic region
amphipathic
the spontaneous movement of a substance down its concentration gradient, from a region where it is more concentrated to a region where it is less concentrated
diffusion
the cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane
exocytosis
an ion transport protein that generates voltage across a membrane
electrogenic pump
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 electric force)
electrochemical gradient
the currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids
fluid mosaic model
limp; lacking in stiffness or firmness, as in a plant cell in surroundings where there is no tendency for water to enter the cell
flaccid
the spontaneous passage of molecules or ions across a biological membrane with the assistance of specific transmembrane transport proteins
facilitated diffusion
cellular uptake of biological molecules and particulate matter via formation of new vesicles from the plasma membrane
endocytosis
the coupling of the “downhill” diffusion of one substance to the “uphill” transport of another against its own concentration gradient
cotransport
lipids with covalently attached carbohydrates
glycolipids
a protein with one or more carbohydrates covalently attached to it
glycoproteins
transmembrane protein channels that open or close in response to a particular stimulus
gated channels
referring to a solution that, when surrounding a cell, will cause the cell to take up water
hypotonic
referring to a solution that, when surrounding a cell, will cause the cell to lose water
hypertonic
transmembrane protein channels that allow a specific ion to flow across the membrane down its concentration gradient
ion channels
typically a transmembrane protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on either side of the membrane (or lining the channel in the case of a channel protein)
integral proteins
referring to a solution that, when surrounding a cell, has no effect on the passage of water into or out of the cell
isotonic
a molecule that binds specifically to another molecule, usually a larger one
ligands
a type of endocytosis in which large particulate substances are taken up by a cell
phagocytosis
a phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment
plasmolysis
the diffusion of a substance across a biological membrane with no expenditure of energy
passive transport
proteins loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer
peripheral proteins
an active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient, generating a membrane potential in the process
proton pump
a type of endocytosis in which the cell ingests extra cellular fluid and its dissolved salutes
pinocytosis
the diffusion of water across a selectively permeable membrane
osmosis
regulation of solute concentrations and water balance by a cell or organism
osmoregulation
a property of biological membranes that allows them to regulate the passage of substances
selective permeability
transmembrane proteins that help a certain substance or class of closely related substances to cross the membrane
transport proteins
swollen or distended, as in plant cells
turgid
a transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell
sodium-potassium pump
