Ch 12 - Transport Across Cell Membranes Flashcards
action potential
traveling wave of electrical excitation caused by rapid, transient, self-propagating depolarization of the plasma membrane in a neuron or other excitable cell; also called a nerve impulse
active transport
the movement of a solute across a membrane against its electrochemical gradient; requires an input of energy, such as that provided by ATP hydrolysis
antiport
type of coupled transport that transfers two different ions or small molecules across a membrane in opposite directions, either simultaneously or in sequence
axon
long, thin extension that conducts electrical signals away from a nerve cell body toward remote target cells
Ca2+ pump (Ca2+ ATPase)
an active transporter that uses energy supplied by ATP hydrolysis to actively expel Ca2+ from the cell cytosol
channel
a protein that forms a hydrophilic pore across a membrane, through which selected small molecules or ions can passively diffuse
dendrite
short, branching structure that extends from the surface of a nerve cell and receive signals from other neurons
depolarization
a shift in the membrane potential, making it less negative on the inside of the cell
electrochemical gradient
driving force that determines which way an ion will move across a membrane; consists of the combined influence on the ion’s concentration gradient and the membrane potential
gradient-driven pump
a protein that uses energy stored in the electrochemical gradient of ions to actively transport a solute across a membrane
H+ pump (H+ ATPase)
a protein or protein complex that uses energy supplied by ATP hydrolysis, an ion ingredient, or light to actively move protons across a membrane
ion channel
transmembrane protein that forms a pore across the lipid bilayer through which specific inorganic ions can diffuse down their electrochemical gradients
K+ leak channel
ion channel permeable to K+ that randomly flickers between an open and closed state; largely responsible for the resting membrane potential in animal cells
ligand-gated channel
an ion channel that is stimulated to open by the binding of a small molecule such as a neurotransmitter
mechanically-gated channel
an ion channel that allows the passage of select ions across a membrane in response to a physical perturbation
membrane potential
voltage difference across a membrane due to a slight excess of positive ions on one side and of negative ions on the other
membrane transport protein
any transmembrane protein that provides a passageway for the movement of select substances across a cell membrane
Na+ pump (Na+ - K+ ATPase)
transporter found in the plasma membrane of most animal cells that actively pumps Na+ out of the cell and K+ in, using the energy derived from ATP hydrolysis
Nernst equation
an equation that relates the concentrations of an inorganic ion on the two sides of a permeable membrane to the membrane potential at which there would be no net movement of the ion across the membrane
nerve terminal
structure at the end of an axon that signals to another neuron or target cell
neuron
an electrically excitable cell that integrates and transmits information as part of the nervous system; a nerve cell
neurotransmitter
small signaling molecule secreted by a nerve cell at a synapse to transmit information to a postsynaptic cell. examples include acetylcholine, glutamate, GABA and glycine
optogenetics
technique that uses light to control the activity of neurons into which light-gated ion channels have been artificially introduced
osmosis
passive movement of water across a cell membrane from a region where the concentration of water is high (because the concentration of solutes is low) to a region where the concentration of water is low (and the concentration of solutes is high)
passive transport
the spontaneous movement of a solute down its concentration gradient across a cell membrane via a membrane transport protein, such as a channel or a transporter
patch-clamp recording
technique used to monitor the activity of ion channels in a membrane; involves the formation of a tight seal between the tip of a glass electrode and a small region of cell membrane, and manipulation of the membrane potential by varying the concentrations of ion in the electrode
pump
transporter that uses a source of energy, such as ATP hydrolysis or sunlight, to actively move a solute across a membrane against its electrochemical gradient
resting membrane potential
voltage difference across the plasma membrane when a cell is not stimulated
symport
a transporter that transfer two different solutes across a cell membrane in the same direction
synapse
specialized junction where a nerve cell communicates with another cell (such as a nerve cell, muscle cell or gland cell), usually via a neurotransmitter secreted by the nerve cell
synaptic vesicle
small membrane-enclosed sac filled with neurotransmitter that releases its contents by exocytosis at a synapse
transmitter-gated ion channel
transmembrane receptor protein or protein complex that opens in response to the binding of a neurotransmitter, allowing the passage of a specific inorganic ion; its activation can trigger an action potential in a postsynaptic cell
transporter
membrane transport protein that moves a solute across a cell membrane by undergoing a series of conformational changes
voltage-gate channel
channel protein that permits the passage of selected ions, such as Na+, across a membrane in response to changes in the membrane potential. found primarily in electrically excitable cells such as nerve and muscle cells
voltage-gated Na+ channel
protein in the plasma membrane of electrically excitable cells that opens in response to membrane depolarization, allowing Na+ to enter the cell. it is responsible for action potentials in these cells
