Ion channel

An ion channel is a membrane protein that forms a pore through which selected ions cross a cell membrane, often in response to voltage, ligands, or mechanical force.

Channel gating: Channel gating is the opening and closing of an ion channel in response to specific signals. Gating determines when this channel permits ions to cross.
Cell membrane: A selectively permeable boundary surrounding a cell, composed mainly of lipids and proteins. Channels function by providing controlled pathways across this lipid barrier.
Action potential: An action potential is a brief, propagating change in a cell’s membrane voltage. Rapid channel opening and closing generates and propagates this electrical signal.
Ion pump: An ion pump uses an energy source to move ions across a membrane, often against their electrochemical gradients. Unlike a channel, a pump actively transports ions rather than providing a passive pore.
Ion selectivity: Ion selectivity is the preference of a pore or transporter for particular ions over others. The channel’s pore discriminates among ions despite their similar sizes.
Electrochemical gradient: An electrochemical gradient is the combined difference in ion concentration and electrical potential across a membrane. It supplies the driving force for ions moving through an open channel.
Synaptic transmission: Synaptic transmission is the communication of signals between neurons or between a neuron and another cell. Postsynaptic channels turn neurotransmitter release into changes in cell voltage.
Carrier protein: A carrier protein binds specific molecules or ions and changes shape to transport them across a membrane. Carriers alternate access through conformational changes instead of forming an open aqueous pore.
Voltage-gated ion channel: A voltage-gated ion channel opens or closes in response to changes in membrane voltage. This channel subtype converts electrical changes into selective ion flow.
Membrane potential: Membrane potential is the voltage difference between the inside and outside of a cell. Voltage-sensitive channels respond to, and help change, this difference.

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