Chapter 5 Flashcards
(22 cards)
A property of biological membranes that allows them to regulate the passage of substances across them
Selective permeability
Having both a hydrophilic and hydrophobic region
Amphipathic
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
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 one or both sides of the membrane
Integral proteins
A protein loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer
Peripheral proteins
A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane
Transport proteins
A type of transport protein in the membrane whose role is to pass large molecules (ions, sugars, and amino acids) that cannot go through the membrane
Channel proteins
A type of transport proteins that hold on to passengers and change their shape to shuttle molecules across the membrane
Carrier proteins
A channel protein in the plasma membrane of a plant, animal, or microorganism call that specifically facilitates osmosis, the diffusion of free water across a membrane
Aquaporin
The random thermal motion of particles of liquids, gases, or solids. In the presence of a concentration or electrochemical gradient, this results in the net movement of a substance from a region where it is more concentrated to a region where it is less concentrated
Diffusion
The diffusion of free water molecules across a selectively permeable membrane
Osmosis
A region along which the density of a chemical substance increases or decreases
Concentration gradient
The diffusion of a substance across a biological membrane with no expenditure of energy
Passive transport
The passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure
Facilitated diffusion
The movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins and requiring an expenditure of energy
Active transport
The ability of a solution surrounding a cell to cause that cell to gain or lose water
Tonicity
The difference in electrical charge across a cell’s plasma membrane due to the differential distribution of ions. Affects the activity of excitable cells and the transmembrane movement of all charged substances
Membrane potential
An active transport protein that generates voltage across a membrane while pumping ions
Electrogenic pump
The coupling of downhill diffusion of one substance to the uphill transport of another against its own concentration gradient
Cotransport
The cellular secretion of biological molecules by the fusion of vesicles containing them to the plasma membrane
Exocytosis
Cellular uptake of biological molecules and articulate matter via formation of vesicles from the plasma membrane
Endocytosis
