Which of the following organic molecules contains both an amine and a carboxyl group?

Lipids primarily consist of fatty acids and glycerol, which do not contain both amine and carboxyl groups. Instead, lipids are characterized by long hydrocarbon chains or rings and typically feature ester bonds rather than the amine and carboxyl functionalities found in amino acids. Thus, lipids lack the necessary groups to qualify as containing both.

Cellulose is a polysaccharide composed of glucose units linked by glycosidic bonds. While it is an important structural component in plant cell walls, it does not contain an amine group or a carboxyl group. Cellulose's structure consists solely of repeating sugar units, which do not include the necessary functional groups found in proteins.

Chitin is a polymer made up of N-acetylglucosamine units, primarily serving as a structural component in the exoskeletons of arthropods and the cell walls of fungi. Although it contains an amine group in the form of the acetylated amino sugar, it lacks a free carboxyl group, which is essential for the question. Therefore, chitin does not meet the criteria specified.