Chapter 5: Cell Membranes and Signaling
Terms in this set (50)
The energy-dependent transport of a substance across a biological membrane against a concentration gradientÑthat is, from a region of low concentration (of that substance) to one of high concentration. (See also passive transport.)
Regulation of the activity of a protein (usually an enzyme) by the binding of an effector molecule to a site other than the active site.
A transport protein in plant and animal cell membranes through which water passes by osmosis. Also called a water channel protein.
A chemical signal that binds to and affects the cell that makes it. (Contrast with paracrine.)
cAMP (cyclic AMP)
A compound formed from ATP that acts as a second messenger.
Membrane proteins that bind specific molecules and transport them through the membrane.
Communication between cells or within cells as they respond to specific cues.
An integral membrane protein that forms an aqueous passageway across the membrane in which it is inserted and through which specific solutes may pass.
Random movement of molecules or other particles, resulting in even distribution of the particles when no barriers are present.
A process by which liquids or solid particles are taken up by a cell through invagination of the plasma membrane. (Contrast with exocytosis.)
Membrane-enclosed compartment in a cell that is formed after endocytosis.
A process by which a vesicle within a cell fuses with the plasma membrane and releases its contents to the outside. (Contrast with endocytosis.)
Passive movement through a membrane involving a specific carrier protein; does not proceed against a concentration gradient. (Contrast with diffusion.)
fluid mosaic model
A molecular model for the structure of biological membranes consisting of a fluid phospholipid bilayer in which suspended proteins are free to move in the plane of the bilayer.
A membrane protein that changes its three-dimensional shape, and therefore its ion conductance, in response to a stimulus. When open, it allows specific ions to move across the membrane.
A lipid to which sugars are attached.
A protein to which sugars are attached.
A membrane protein involved in signal transduction; characterized by binding GDP or GTP.
G protein-linked receptors
A class of receptors that change configuration upon ligand binding such that a G protein binding site is exposed on the cytoplasmic domain of the receptor, initiating a signal transduction pathway.
A chemical substance produced in minute amounts by endocrine cells and transported in the blood to distant target cells, where it exerts regulatory influences on their function.
Having a greater solute concentration. Said of one solution compared with another. (Contrast with isotonic.)
Having a lesser solute concentration. Said of one solution in comparing it to another. (Contrast with isotonic.)
integral membrane proteins
Proteins that are at least partially embedded in the plasma membrane. (Contrast with peripheral membrane proteins.)
An integral membrane protein that allows ions to diffuse across the membrane in which it is embedded.
Having the same solute concentration; said of two solutions. (Contrast with hypotonic.)
A type of cell signal that requires that the signaling and responding cells are in direct contact. Usually involves interaction between signaling molecules bound to the surfaces of the two cells.
Any molecule that binds to a receptor site of another (usually larger) molecule.
Movement of water across a differentially permeable membrane, from one region to another region where the water potential is more negative.
Pressure exerted by the flow of water through a semipermeable membrane separating two solutions with different concentrations of solute.
Pertaining to a chemical signal, such as a hormone, that acts locally, near the site of its secretion. (Contrast with autocrine.)
Diffusion across a membrane; may or may not require a channel or carrier protein. (Contrast with active transport.)
peripheral membrane proteins
Proteins associated with but not embedded within the plasma membrane. (Contrast with integral membrane proteins.)
Endocytosis by a cell of another cell or large particle.
A lipid containing a phosphate group; an important constituent of cellular membranes. (See lipid.)
Endocytosis by a cell of liquid containing dissolved substances.
pressure potential (?p)
The hydrostatic pressure of an enclosed solution in excess of the surrounding atmospheric pressure. (Contrast with solute potential, water potential.)
primary active transport
Active transport in which ATP is hydrolyzed, yielding the energy required to transport an ion or molecule against its concentration gradient. (Contrast with secondary active transport.)
An enzyme that catalyzes the addition of a phosphate group from ATP to a target protein.
A glycoprotein containing a protein core with attached long, linear carbohydrate chains.
sensory receptor cell.
Endocytosis initiated by macromolecular binding to a specific membrane receptor. Also called receptor-mediated endocytosis.
secondary active transport
A form of active transport that does not use ATP as an energy source; rather, transport is coupled to ion diffusion down a concentration gradient established by primary active transport. (Contrast with primary active transport.)
To discharge a substance from a cell or gland.
Allowing certain substances to pass through while other substances are excluded; a characteristic of membranes.
sensory receptor cell
A cell, typically a neuron, that is specialized to transform the energy of a stimulus into an electric signal. Each type is highly specific in the stimuli to which it ordinarily responds.
signal transduction pathway
The series of biochemical steps whereby a stimulus to a cell (such as a hormone or neurotransmitter binding to a receptor) is translated into a response of the cell.
Diffusion that doesnÕt involve a direct input of energy or assistance by carrier proteins.
sodiumÐpotassium (Na+-K+) pump
A membrane protein (anti-porter) that carries out primary active transport of ions; it uses energy from ATP to pump sodium ions out of a cell and potassium ions into the cell. Also called a sodiumÐpotassium ATPase.
An integral membrane protein that spans the phospholipid bilayer.
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