Ion channel

Ion channelorIon channel(: ion channel) is a kind of membrane penetration in (and inner membrane, etc.), is a generic term for proteins passively pass through. In addition to maintaining and changing the cells, it also conducts ions into and out of cells. Such as generation of electrical excitable cells, generation of receptor potential in sensory cells, maintenance of resting membrane potential in cells, and the like.

table of contents

principle

Ions that have large energy to enter small oils, are hard to enter oil. For this reason it can hardly penetrate biological membranes of the part composed of. In biological membranes, ion channels are membrane proteins that provide pathways (channels) through which ions pass. Ions flow through pores, but many channels have a structure called a gate in the middle. The gate takes two states, a closed state and an opened state, and permits ions to pass only when it is open.

Ion selectivity

The selectivity of ions varies depending on the channel, and there are ion channels that selectively transmit only one type of ion, and ion channels that pass many types of cations. Due to ion selectivity, it is called. The ion channel transmits ions from higher to lower. In the case of cells, the gradient is the sum of the gradient of the chemical potential due to the ion concentration difference inside and outside the membrane and the gradient of the electric potential by the membrane potential. That is, the flow direction is determined by the balance between the tendency of flowing from the higher concentration to the lower concentration and the balance of the tendency to move in the negative direction in the case of positive ions. There is also an inward rectifying channel that permits ions to penetrate inward of the cell, but it is difficult to transmit outwardly.

Control style

There are several control modes of ion channel opening and closing.

Voltage dependence

It opens and closes according to. Many channels have a plurality of gates with different time constants and perform specific opening and closing depending on time when the membrane potential changes. Ligand dependence

Those that are opened by specific binding of molecules. In this case the ion channel itself is covered. From the side of the receptor it can also be called an ion channel-coupled receptor. For example,. Mechanical stimulus dependence

It opens when a mechanical deformation or force is applied to a channel molecule. Tactile sense, hearing sense, gravity sense and so on. Hair cells and others are famous. Temperature dependence

Thing due to temperature. Depending on the type, the temperature which is easy to open is decided. Leakage channel

It is normally open and sinks in a way that leaks certain ions little by little. Phosphorylation dependence

It is due to a phosphorylation signal from other proteins.

Other transport proteins

It is a protein that transports ions "actively" using proteins such as ions that move. While this is a protein similar to ion channels in terms of ion selectivity and transport to the inside and outside of the membrane, while the pump can actively transport ions against the electrochemical potential gradient, ions A channel can only move "passively" in a lower direction. There are also ion exchangers that transport multiple types of ions in the opposite direction at certain number ratios, and co-transporters that transport in the same direction.

footnote

1. *: voltage-dependent channel, voltage-gated channel 2. : ligand-gated channel 3. ***: mechanosensitive channel

Related item

• • • • • • • \ - Includes voltage-dependent anion channels
• (Water channel) *

External link

• • Items on "ion channels" in \ -. (English)
• \ - It is responsible for the mechanism of opening and closing of voltage-gated ion channels.
• \ - An indication of ease of opening of ion channels, variables concerning the number of ion channels, single channel current and variables defining the ion current amount of the biological membrane.
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Post Date : 2018-02-22 01:00

This article is taken from the Japanese Wikipedia Ion channel

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