Look over other homework problems for mechanism of Valium and other concepts. Receptors are generally transmembrane proteins, as are transport proteins for taking in food and excreting waste. You should be generally familiar with the list of membrane properties on page 264.
Pumps mediate active transport, and channels are involved with passive transport.
The acetylcholine receptor is located on the postsynaptic membrane in cholinergic nerves. Acetylcholine is released from the presynaptic membrane in response to depolarization. Acetylcholinesterase normally hydrolyzes acetylcholine very rapidly, so that the response lasts only about a millisecond. Acetylcholinesterase is anchored to the postsynaptic membrane by a glycolipid attachment but is not part of the receptor. The acetylcholine receptor is described in detail, and you should understand the details of what it looks like and how it works.