Final answer:
Chemically gated channels in the plasma membrane open or close in response to specific chemicals like neurotransmitters binding to them, allowing ions to pass through and change the membrane's charge.
Step-by-step explanation:
The type of active channels in the plasma membrane that open or close when they bind certain chemicals, such as neurotransmitters, are known as chemically gated channels. These channels have a specific site where the neurotransmitter, acting as a ligand, can bind. This action triggers the gateway of the channel to open, permitting select ions, such as sodium (Na+), calcium (Ca2+), and potassium (K+), to flow through.
When neurotransmitters like acetylcholine bind to the extracellular surface of the channel protein, the configuration of the channel changes and the pore opens. This allows for the ions to pass through, resulting in changes in the charge across the cell's membrane. Such changes are crucial for the propagation of electrical signals in neuronal communication and muscle contraction.