Which statement correctly describes a quality of acetylcholine?

Which statement correctly describes a quality of acetylcholine?

• A. Very short duration of action and cannot be taken orally
• B. Long duration of action and well absorbed orally
• C. Stable in gastric acid
• D. Non-polar and lipid-insoluble

Answer: (A)

Acetylcholine is rapidly inactivated by enzymes, so its signaling is extremely short-lived. In the synaptic cleft, acetylcholinesterase quickly hydrolyzes it, which means the action terminates in a fraction of a second. That same rapid metabolism makes it unable to be given orally: the molecule is a quaternary ammonium compound, highly polar and water-soluble, so it does not cross the gut lining and would be destroyed before it could reach receptors. So the statement that it has a very short duration and cannot be taken orally captures both the rapid termination of its action and its poor oral bioavailability. The other ideas don’t fit: a long duration would require resistance to hydrolysis, which acetylcholine doesn’t have; being stable in gastric acid would imply it withstands stomach conditions, which it does not because it’s quickly degraded by esterases; and while it is lipid-insoluble, it is not non-polar—it's highly polar due to its charged quaternary ammonium group, so describing it as non-polar is inaccurate.

Acetylcholine is rapidly inactivated by enzymes, so its signaling is extremely short-lived. In the synaptic cleft, acetylcholinesterase quickly hydrolyzes it, which means the action terminates in a fraction of a second. That same rapid metabolism makes it unable to be given orally: the molecule is a quaternary ammonium compound, highly polar and water-soluble, so it does not cross the gut lining and would be destroyed before it could reach receptors. So the statement that it has a very short duration and cannot be taken orally captures both the rapid termination of its action and its poor oral bioavailability.

The other ideas don’t fit: a long duration would require resistance to hydrolysis, which acetylcholine doesn’t have; being stable in gastric acid would imply it withstands stomach conditions, which it does not because it’s quickly degraded by esterases; and while it is lipid-insoluble, it is not non-polar—it's highly polar due to its charged quaternary ammonium group, so describing it as non-polar is inaccurate.