What type of channel opens in response to a specific chemical signal?

A ligand-gated channel opens in response to a specific chemical signal, such as a neurotransmitter or hormone, binding to its receptor. This binding results in a conformational change in the channel protein, allowing ions like sodium, potassium, or calcium to flow across the cell membrane. This mechanism is crucial for various physiological processes including synaptic transmission in neurons and muscle contraction, as it regulates the flow of ions in response to external signals.

In contrast, voltage-gated channels open in response to changes in membrane potential, leak channels allow ions to passively diffuse down their concentration gradient without external signals, and passive channels also refer to channels that allow ions to flow due to diffusion, rather than being opened by a ligand. Therefore, the correct identification of the ligand-gated channel highlights its unique function in the context of cellular signaling processes.