Ion Channel Receptor
Phagocytosis and pinocytosis are the two basic kinds of endocytosis used by even the most primitive of organisms, but just as exocytosis can be triggered by a signal, there is another category of endocytosis that works a similar way: receptor-mediated. One type of the receptor-based category uses the ion channel receptor.
Ion channel receptors are transmembrane channel proteins that are fitted with pores (or channels) through which ions can flow. They have a gate that opens and closes to help the cell regulate entry.
The ion channel receptor opens in response to a ligand, a special substance that triggers an electric reaction in the channel protein once it chemically binds with it to cause endocytosis. Ligands can be a variety of substances, including hormones (a molecule that triggers activity in a cell) or neurotransmitters (chemicals that carry information through the neural network to enable center-controlled action, like a brain causing movement in a human). The gate opens for a short time, after which the ligand’s effect on the channel protein wears off and the ligand detaches itself from the ion channel receptor. The process can be repeated with another ligand so that the channel can be reopened when the cell is need of another ion. In most cases, the ion flow rate is high.
Specific ion channels allow the entry of specific types of ions by way of gates that don’t open for the wrong type of ion, and certain ligands induce the signal pathway into the cell with certain ion channel receptors. In a given living cell, there are over 300 different types of ion channel receptors, and these receptors can be classified based upon the type and intensity of the voltage generated by the channel once it chemically interacts with its ligand, the type of ligands it binds with, by the type of gates the channel receptor uses, by the type of ions it opens for, or the channel’s location in the plasma membrane. Ion channel receptors are abundant and essential in electrically excitable cells (like neurons), but they are present in the cell membranes of almost all living cells. As such, they have a role in the functioning of the neural network and also in rapid changes in cells like muscle contraction, white blood cell (pathogen-fighting cell) activation, etc.
Ion channel receptors are transmembrane, integral membrane, channel proteins that are responsible for a type of receptor-mediated endocytosis. A specific type of ligand binds chemically with a specific type of ion channel receptor to induce a reaction that generates an electrical signal pathway. This pathway opens the gate of the channel protein to allow a specific type of ion to pass through. Ion channel receptors are present in just about all living cells; they are most abundant in and essential to nerve cells, called neurons. Their biological significance is most evident in the functioning of the nervous system (in the more advanced lifeforms that have such) and also in the rapid changes of cells.