Final answer:
Ligand-gated ion channels open in response to the binding of a signaling molecule, such as a neurotransmitter, to the channel, allowing ions to flow through the membrane and alter the cell's charge. The answer is option C.
Step-by-step explanation:
The type of ion channel that opens in response to binding to another protein is the ligand-gated ion channel. These channels are also known as ionotropic receptors and they function by allowing ions to cross the membrane, changing its electromagnetic charge.
When a ligand, such as a neurotransmitter, binds to the extracellular region of the channel, the channel opens to permit the flow of specific ions such as sodium, calcium, and potassium. This process is integral for neural communication, allowing for rapid response to signaling molecules.