Answer;
-COOH
Explanation;
The carboxyl group includes both a keto oxygen and a hydroxyl group; Carboxyl groups are weak acids, dissociating partially to release hydrogen ions. The carboxyl group (symbolized as COOH) has both a carbonyl and a hydroxyl group attached to the same carbon atom, resulting in new properties.
The carboxyl functional group is an acidic functional group frequently found in biological molecules. It is found in amino acids, proteins. fatty acids, acetic acids and other organic acids.