Question

Ion channels are transmembrane proteins that allow the rapid passage of ions across membranes. They have exquisite specificity and can selectively open or close. The opening and closing is a process known as gating. Distinguish the following types of channels:

1. Ligand-gated channels
2. Signal-gated channels
3. Voltage-gated channels
4. Mechanoselective channels

Answer 1

Topics	Ligand gated channels	Signal gated channels	Voltage gated channels	Mechanoselective channels
Function	They are transmembrane protein complexes that conduct ion flow through a channel pore in response to the binding of a neurotransmitter.	Their functions include establishing a resting membrane potential and other electrical signals by gating the flow of ions across cell membrane, controlling the flow of ions across secretory and epithelial cells, regulating cell volume.	They are transmembrane proteins that play important roles in electrical signalling of cells.	They alter the membrane conformation between an open and closed state during mechanical deformations.
Location	At the sites of synaptic contact are predominantly on dendritic spines, dendrites and somata of nerve cells or neurons.	Seen in neuromuscular junction	Axon and at the synapse	Stereocilia of the inner ear
Open in response	Ligand(some chemical signal)binding to them.	Signals whose receptors are gated ion channels	Voltage(when the cell gets depolarized)	Physical distotion of the cell membrane
Driven force	Electrochemical gradient	Concentation gradient	Changes in electric membrane potential	Conductive force
Example	Nicotinic cholinergic, 5 hydroxytryptamine	Acetylcholine and serotonin	In heart allowing for the rapid and coordinate myocyte depolarization and repolarization required for efficient electromechanical coupling.	Mechanoselective calciumchannel in plasma membrane, which can be amplified through release of internal pores especially from vacuole like through two pore channel to maintain membrane integrity and ion homeostasis.
Selectivity	less selective which allow two or more types of ions to pass through the channel pore	Allow millions of ions from one side of membrane to other	More selective which allow only one type of ion to permeate	Vary in selectivity for permeating ions from non selective between anions and cations
Active or Passive	Passive	Passive	Active	Active