A protein channel is a passage through a cell membrane used for communication between the outside and inside of a cell. Protein channels are the cells control system. Transporting water, chemical and electric signals, they affect the function of the cell by controlling growth and metabolism. Specialized protein channels transport calcium, sodium and other ions to change the electrical potential across cell membranes causing the cells to react to stimuli.
Anatomy of a Protein Channel
Cells membranes consist two layers of lipids called the lipid bilayer. Protein channels are formed by plasma proteins entering through the lipid membranes of the cell. Depending on the molecular make-up of the plasma protein, the protein channel may have different chemical and physical qualities, these qualities determine the function of the protein channel. Protein channels are small and only allow small molecules and ions to pass.
Protein channels are like transport highways into and out of the cell body. Regulation of movement through the channels is regulated by areas on the cell called receptors. Neurotransmitters attach to the cell receptors and open and close the channels allowing for movement of substances into and out of the cells. Sodium channels utilize the neurotransmitter acetylcholine to regulate the intake of sodium ions. When the cell receptors are vacant, ions are allowed to enter the cell. However, when acetylcholine is binding to the receptors, the channel closes preventing ions from passing.
Protein channels have many different classifications depending on their actions and purposes. According to the Nephrogenic Diabetes Insipidus Foundation (NDIF), fast channels are gated, voltage activated channels with lower activation potential than the slower activating channels. Sodium ion channels are fast-acting channels responsible for activation of nerve cells throughout your body.
Calcium protein channels are considered slow-gated channels. NDIF describes slow-gated calcium channels as being more sensitive to calcium ions as opposed to sodium ions. There are three different subtypes of calcium channels throughout your body; each one reacts differently by releasing different types of neurotransmitters affecting smooth muscle control. The difference in the reaction speed between fast-gated sodium channels and slow-gated calcium channels is required because nerve impulses require a more immediate response than smooth muscle.