Question

which of the following organic molecules contain both an amine and carboxyl group?
cellulose
chitin
lipids
proteins

Explanation:

• Cellulose: It is a polysaccharide (carbohydrate) composed of glucose units. Its functional groups mainly include hydroxyl (-OH) groups. There are no amine (-NH₂) or carboxyl (-COOH) groups.
• Chitin: It is a polysaccharide. It has an acetylated amino group (-NH - CO - CH₃) but no free carboxyl group (-COOH).
• Lipids: Lipids have functional groups such as ester (-COO -) groups (in triglycerides, for example). There are no amine (-NH₂) and carboxyl (-COOH) groups in the same molecule in a typical lipid structure relevant to this question.
• Proteins: Proteins are made up of amino acids. Amino acids have a general formula \(NH_2 - CH(R)-COOH\). So, proteins, being polymers of amino acids, contain both amine (-NH₂) groups (from the amino - terminal of amino acids and side - chain amines in some amino acids like lysine) and carboxyl (-COOH) groups (from the carboxyl - terminal of amino acids and side - chain carboxyls in some amino acids like aspartic acid and glutamic acid).

Answer:

Proteins