Answer:
The correct answer is
18
Groups of the periodic table: The s-, p-, and d-block elements of the periodic table are arranged into 18 numbered columns, or groups.
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Answer:
They are opened either by the binding of ligands or by changes in electric potential across the membrane
Explanation:
Ion channels are the integral membrane proteins that form pores or holes for the transport of specific ions, such as potassium ions (K+), Na+, etc. Most ion channels are selective and allow only a single type of ion to pass through. These ion channels facilitate the diffusion of ions down the concentration gradient and do not require ATP.
Ion channels are mostly gated. Some ion channels open in response to change in the concentration of ions and electric charges across the membrane. Some ion channels open and close in response to the binding of specific molecules called a ligand. For example, binding of two molecules of acetylcholine to the receptor on the motor endplate of a neuromuscular junction opens an ion channel in the ACh receptor through which Na+ can flow across the membrane.
