oteins line channel. Small molecules or ions of the right shape, size, and charge can pass through the channel. The charges in the hydrophilic part of the channel protein determine which typed of ions can pass through the channel.
             The function of a channel protein is determined by its shape. The channel can be open or closed, depending on the shape of the channel proteins. Some channel proteins change shape to open the channel when a ligand binds to a specific receptor site on the protein. This is called a ligand-gated channel. Other channel proteins change shape to open the channel when there is a change in charge across the cell membrane. This is called a voltage-gated channel.
             Receptor molecules are proteins in the cell membrane with an exposed binding site on the outer cell surface, which can attach to specific ligand molecules. The receptors and the ligands they bind are part of an intercellular communication system that controls coordination of cell activities. The binding acts as a signal that trigg
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