Complex sentence: An acetylcholine receptor (abbreviated AChR) is an integral membrane protein that responds to the binding of the neurotransmitter acetylcholine by opening a pathway in the membrane for the diffusion of ions across the cell membrane.
Split into simpler sentences: An acetylcholine receptor (abbreviated AChR) is an integral membrane protein that responds to the binding of the neurotransmitter acetylcholine. Nicotinic ACh receptors respond to acetylcholine by opening a channel to allow diffusion of ions across the cell membrane.