In vertebrates, motor neurons release acetylcholine (ACh), a small molecule neurotransmitter, which diffuses across the synaptic cleft and binds to nicotinic acetylcholine receptors (nAChRs) on the cell membrane of the muscle fiber, also known as the sarcolemma.
The amino acids code for the protein. If one amino acid is changed then the whole protein is changed.
B or d.... hope this helps:)
