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Related Concept Videos

Electrochemical Gradient and Channel Proteins: An Overview01:21

Electrochemical Gradient and Channel Proteins: An Overview

4.1K
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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Ion Channels01:19

Ion Channels

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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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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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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...
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Ligand-gated Ion Channels01:19

Ligand-gated Ion Channels

13.8K
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...
13.8K
Mechanically-gated Ion Channels01:12

Mechanically-gated Ion Channels

7.4K
Mechanically-gated ion channels are proteins found in eukaryotic and prokaryotic cell membranes that open in response to mechanical stress. Tension, compression, swelling, and shear stress can alter the conformation of the protein, opening a transmembrane channel that allows the passage of ions for signal transmission. In eukaryotes, mechanically-gated channels are distributed in several regions like the neurons, lungs, skin, bladder, and heart, where they play critical roles in numerous...
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Related Experiment Video

Updated: Dec 20, 2025

Determination of the Relative Cell Surface and Total Expression of Recombinant Ion Channels Using Flow Cytometry
11:32

Determination of the Relative Cell Surface and Total Expression of Recombinant Ion Channels Using Flow Cytometry

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Proteins, channels and crowded ions.

Bob Eisenberg1

  • 1Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.

Biophysical Chemistry
|March 21, 2003
PubMed
Summary

Ion channel selectivity arises from high-density fixed charges within the pore, influencing ion flow and protein function. Physical chemistry calculations explain these complex channel properties.

Area of Science:

  • Biophysics
  • Physical Chemistry
  • Molecular Biology

Background:

  • Ion channels are crucial proteins controlling biological functions and are implicated in various diseases.
  • Channel selectivity, determined by the open pore structure, governs ion transport.
  • Predicting channel function from structure using physical laws is a significant scientific challenge.

Purpose of the Study:

  • To investigate the role of fixed charges and counter-ion crowding in ion channel selectivity.
  • To apply physical chemistry principles to model ion channel behavior.
  • To explain the experimentally observed selectivity and complex properties of ion channels.

Main Methods:

  • Modeling the L-type calcium channel using physical chemistry principles.

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One-channel Cell-attached Patch-clamp Recording
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One-channel Cell-attached Patch-clamp Recording

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Proteomics to Identify Proteins Interacting with P2X2 Ligand-Gated Cation Channels
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Proteomics to Identify Proteins Interacting with P2X2 Ligand-Gated Cation Channels

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Related Experiment Videos

Last Updated: Dec 20, 2025

Determination of the Relative Cell Surface and Total Expression of Recombinant Ion Channels Using Flow Cytometry
11:32

Determination of the Relative Cell Surface and Total Expression of Recombinant Ion Channels Using Flow Cytometry

Published on: September 28, 2016

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One-channel Cell-attached Patch-clamp Recording
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One-channel Cell-attached Patch-clamp Recording

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Proteomics to Identify Proteins Interacting with P2X2 Ligand-Gated Cation Channels
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  • Calculating free energy of salt solutions from infinite dilution to saturation.
  • Analyzing the impact of high counter-ion densities (over 5 molar) in confined channel volumes.

    • Main Results:

    • High energies are required to crowd charges into the ion channel pore.
    • These crowding energies successfully account for substantial ion selectivity.
    • The model explains complex channel properties observed experimentally.

    Conclusions:

    • Fixed charges and their associated counter-ion clouds are key determinants of ion channel selectivity.
    • The principles governing crowded charges in channels may apply to proteins broadly.
    • Understanding these physical interactions advances knowledge of channel function in health and disease.