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Related Concept Videos

Ion Channels01:19

Ion Channels

92.0K
The movement of ions like sodium, potassium, and calcium into and out of the cell is essential to maintain the electrochemical gradient in living cells. The ion channels—a class of membrane transport proteins—help maintain this ionic gradient for the smooth functioning of physiological activities such as maintaining cell size and volume, conducting nerve impulses, and gas and nutrient exchange.
Ion channels are specialized integral membrane proteins on the plasma membrane that allow...
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Voltage-gated Ion Channels01:26

Voltage-gated Ion Channels

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Voltage-gated ion channels are transmembrane proteins that open and close in response to changes in the membrane potential. They are present on the membranes of all electrically excitable cells such as neurons, heart, and muscle cells.
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
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Non-gated Ion Channels01:24

Non-gated Ion Channels

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Ion channels are specialized proteins on the plasma membrane that allow charged ions to pass down their electrochemical gradient. Their main function is to maintain the membrane potential which is critical for cell viability. These channels are either gated or non-gated and can transport more than a thousand ions within milliseconds for the cellular event to occur.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism....
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Electrochemical Gradient and Channel Proteins: An Overview01:21

Electrochemical Gradient and Channel Proteins: An Overview

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An electrochemical gradient is a fundamental concept in biology and chemistry. It regulates the movement of ions across cell membranes. This movement is influenced by two factors:
The electrical gradient: The electrical gradient across cell membranes refers to the difference in electric charge between the inside and outside of a cell.  This difference drives the movement of ions towards or away from the cells. For instance, if the inside of the cell is more negatively charged relative to...
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The Role of Ion Channels in Neuronal Computation01:19

The Role of Ion Channels in Neuronal Computation

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A postsynaptic neuron usually receives numerous impulses from several other presynaptic neurons. The axon hillock of the postsynaptic neuron integrates all these signals and determines the likelihood of firing an action potential.
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential....
4.0K
Ligand-gated Ion Channels01:19

Ligand-gated Ion Channels

14.6K
Ligand-gated ion channels are transmembrane proteins with a channel for ions to pass through and a binding site for a ligand. The channel opens only when a ligand attaches to the binding site.
Three Subfamilies of Ligand-gated Ion Channels
Ligand-gated ion channels fall into three subfamilies. The 'Cys-loop' includes the nicotinic acetylcholine receptors, γ-aminobutyric acid (GABA), glycine, and 5-hydroxytryptamine receptors. The second one is the 'Pore-loop' channels that...
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Updated: Mar 2, 2026

Whole-cell Patch-clamp Recordings for Electrophysiological Determination of Ion Selectivity in Channelrhodopsins
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Whole-cell Patch-clamp Recordings for Electrophysiological Determination of Ion Selectivity in Channelrhodopsins

Published on: May 22, 2017

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Ion channels and ion selectivity.

Benoît Roux1

  • 1Department of Biochemistry and Molecular Biology, University of Chicago, 929 E 57th Street, Chicago, IL 60637, U.S.A. roux@uchicago.edu.

Essays in Biochemistry
|May 11, 2017
PubMed
Summary
This summary is machine-generated.

Ion channels control ion passage across cell membranes. Potassium (K+) channels exhibit remarkable selectivity for K+ over sodium (Na+) ions, crucial for biological membrane excitability.

Keywords:
free energyhydrationmolecular dynamicssolvation

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Area of Science:

  • Biophysics
  • Molecular Biology
  • Cell Physiology

Background:

  • Ion channels and pumps facilitate and regulate ion transport across lipid membranes.
  • Selective ion channels are critical for biological membrane excitability, underpinning phenomena like the action potential.
  • Potassium (K+) channels are vital for maintaining membrane potential due to their high selectivity and conduction rate.

Purpose of the Study:

  • To elucidate the mechanisms underlying the high selectivity of K+ channels for K+ over Na+ ions.
  • To explore the 'knock-on' mechanism of ion permeation through K+ and Na+ channels.
  • To investigate the role of subtle dynamic effects in ion channel selectivity.

Main Methods:

  • Analysis of ion channel structure and function.
  • Theoretical modeling of ion permeation mechanisms.
  • Comparison of K+ and Na+ channel properties.

Main Results:

  • K+ channels achieve high selectivity for K+ over Na+ while allowing rapid ion flux.
  • Ion permeation in K+ channels follows a 'knock-on' mechanism with interspersed water molecules.
  • Na+ channels also utilize a 'knock-on' mechanism, but with less stringent ion dehydration requirements.
  • Subtle dynamic effects, beyond simple structural concepts, are crucial for ion selectivity.

Conclusions:

  • The precise mechanism of ion selectivity in channels involves complex interplay of structure and dynamics.
  • Understanding these mechanisms is key to comprehending cellular excitability and function.
  • Further research into flexible dynamical structures is needed to fully rationalize ion selectivity.