Answer;
-Carboxyl group
Explanation;
-Lipids is one of the four important biomolecules, others being, nucleic acid, carbohydrates, and proteins.
-Lipids are made of glycerol and fatty acids. Fatty acids consist of a carboxylic acid (-C=O-OH functional group) with a long un-branched hydrocarbon chain. Fatty acids serve as a precursor for other lipids and are used by the body for energy storage. Fatty acids may be saturated or unsaturated. Saturated fatty acids have single bonds between each carbon, while unsaturated have either a double or triple bonds.
