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BIOL 3510: CHAPTER 12 KEY TERMS
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an aqueous pore in a lipid membrane, with walls made of protein, through which selected ions or molecules can pass
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axon
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Long thin nerve cell process capable of rapidly conducting nerve impulses over long distances so as to deliver signals to other cells
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active transport
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movement of a molecule across a membrane driven by ATP hydrolysis or another form of metabolic energy.
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action potential
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Rapid, transient, self-propagating electrical signal in the plasma membrane of a cell such as a neuron or muscle. A nerve impulse.
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stress-gated channel
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membrane protein that allows the selective entry of specific ions into a cell and is opened by mechanical force.
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synapse
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specialized junction between a nerve cell and another cell (nerve cell, muscle cell, gland cell) across which the nerve impulse is transferred.
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synaptic vesicles
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small membrane-enclosed sac filled with neurotransmitter that releases its contents by exocytosis at a synapse.
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transporter |
membrane protein that transports ions or molecules across a cell membrane.
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voltage-gated channel
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membrane protein that selectively allows ions such as Na+ (carried by the voltage-gated Na+ channel) to cross a membrane and is opened by changes in membrane potential
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neuron (nerve cell)
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cell with long processes specialized to receive, conduct, and transmit signals in the nervous system.
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neurotransmitter
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small signaling molecule secreted by a nerve cell at a chemical synapse to signal to the postsynaptic cell. Examples include acetylcholine, glutamate, GABA, and glycine.
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osmosis |
net movement of water across a semipermeable membrane driven by a difference in concentration of solute on either side. Membrane must be permeable to water but not solutes.
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osmotic pressure
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pressure that must be exerted on the low-solute concentration side of a semipermeable membrane to prevent the flow of water across the membrane as a result of osmosis.
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passive transport
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the movement of a small molecule or ion across a membrane due to a difference in concentration or electrical charge.
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patch-clamp recording
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technique in which the tip of a small glass electrode is sealed onto a patch of cell membrane, thereby making it possible to record the flow of current through individual ion channels in the patch.
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electrochemical gradient
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driving force that causes an ion to move across a membrane. Caused by differences in ion concentration and in electrical charge on either side of the membrane.
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ligand-gated channel
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an ion channel that opens when it binds a small molecule such as a neurotransmitter.
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coupled transporter
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membrane transport protein that carries out transport in which the transfer of one molecule depends on the simultaneous or sequential transfer of a second molecule.
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Nernst equation
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quantitative expression that relates the equilibrium ratio of concentrations of an ion on either side of a permeable membrane to the voltage difference across the membrane.
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nerve terminal
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the ending of an axon from which signals are sent to adjoining cells, usually at a synapse.
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membrane transport protein
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any protein embedded in a membrane that serves as a carrier of ions or small molecules from one side to the other.
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Na+/K+ pump (sodium pump)
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transmembrane carrier protein, found in the plasma membrane of most animal cells, that pumps NA+ out of the cell and K+ into the cell, using the energy derived from ATP hydrolysis.
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membrane potential
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voltage difference across a membrane due to a slight excess of positive ions on one side and of negative ions on the other.
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