An acetyl group is a functional group in organic chemistry with the formula C2H3O. It consists of a carbonyl group (C=O) attached to a methyl group (CH3). This structure makes it a key component in various biochemical processes and compounds, including acetylcholine, a neurotransmitter important for nerve function. Acetyl groups are commonly found in many organic molecules, including acetic acid and acetylsalicylic acid, which is the active ingredient in aspirin. They play a significant role in metabolism and are involved in the modification of proteins through a process called acetylation, which can affect gene expression and protein function.