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Membrane Transport Proteins
A membrane transport protein (or simply transporter) is a protein involved in the movement of ions, small molecules, or macromolecules, such as another protein across a biological membrane. Any protein embedded in a membrane that serves as a carrier of ions or small molecules from one side to the other. TERM 2
Channels
DEFINITION 2 An aqueous pore in a lipid membrane, with walls made of protein, through which selected ions or molecules can pass. TERM 3
Transporter
DEFINITION 3 Membrane protein that transports ions or molecules across a cell membrane. TERM 4
Passive Transport
DEFINITION 4 Passive transport means moving biochemicals and other atomic or molecular substances across membranes. The movement of a small molecule or ion across a membrane due to a difference in concentration or electrical charge. TERM 5
Active Transport
DEFINITION 5 Active transport is the movement of a substance against its concentration energy (from low to high concentration). Movement of a molecule across a membrane driven by ATP hydrolysis or another form of metabolic energy.
Electrochemical Gradient
An electrochemical gradient is a spatial variation of both electrical potential and chemical concentration across a membrane. 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. TERM 7
Na+-K+ Pump
DEFINITION 7 Na+/K+-ATPase (also known as the Na+/K+ pump, sodium- potassium pump, or simply sodium pump, for short) is an enzyme () located in the plasma membrane (to be specific, an electrogenic transmembrane ATPase) in all animals. Transmembrane carrier protein, found in the plasma membrane of most animal cells, that pumps Na+ out of and K+ into the cell, using the energy derived from ATP hydrolysis. TERM 8
Osmosis
DEFINITION 8 Osmosis is the movement of water molecules through a selectively-permeable membrane down a water potential gradient. Net movement of water molecules across a semipermeable membrane driven by a difference in concentration of solute on either side. The membrane must be permeable to water but not to the solute molecules. TERM 9
Osmotic Pressure
DEFINITION 9 Osmotic pressure is the pressure applied by a solution to prevent the inward flow of water across a semipermeable membrane. 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. TERM 10
Coupled Transporters
DEFINITION 10 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.
Nernst Equation
In electrochemistry, the Nernst equation is an equation that can be used (in conjunction with other information) to determine the equilibrium reduction potential of a half-cell in an electrochemical cell. 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. TERM 17
Neuron
DEFINITION 17 A neuron (also known as a neurone or nerve cell) is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Cell with long processes specialized to receive, conduct, and transmit signals in the nervous system. TERM 18
Axon
DEFINITION 18 An axon is a long, slender projection Long thin nerve cell process capable of rapidly conducting nerve impulses over long distances so as to deliver signals to other cells. TERM 19
Nerve Terminal
DEFINITION 19 A peripheral nerve, or simply nerve is an enclosed, cable-like bundle of peripheral axons (the long, slender projections of neurons). The ending of an axon from which signals are sent to adjoining cells, usually at a synapse. TERM 20
Action Potential
DEFINITION 20 Rapid, transient, self-propagating electrical signal in the plasma membrane of a cell such as a neuron or muscle.
Synapses
Chemical synapses are specialized junctions through which neurons signal to each other and to non-neuronal cells such as those in muscles or glands. Specialized junction between nerve cell and another cell across which the nerve impulse is transferred. In most synapses the signal is carried by a neurotransmitter, which is secreted by the nerve cell and diffuses to the target cell. TERM 22
Neurotransmitter
DEFINITION 22 Neurotransmitters are endogenous chemicals which transmit signals from a neuron to a target cell across a synapse. Small signaling molecule secreted by a nerve cell at a chemical synapse to signal to the postsynaptic cell. TERM 23
Synaptic Vesicles
DEFINITION 23 In a neuron, synaptic vesicles (or neurotransmitter vesicles) store various neurotransmitters that are released at the synapse. Small membrane-enclosed sac filled with neurotransmitter that releases its contents by exocytosis at a synapse.
