Which molecules are typically formed from long chains of amino acids?

• A. Proteins
• B. Carbohydrates
• C. Lipids
• D. Nucleic acids

Answer: (A)

Proteins are built from amino acids linked together into long chains called polypeptides, which then fold into unique three-dimensional shapes to perform a wide range of cellular functions. The idea of “long chains of amino acids” points specifically to proteins, because the sequence and length of these amino acids determine the structure and function of the molecule. The primary structure is the actual order of amino acids; this dictates how the chain will fold into secondary, tertiary, and sometimes quaternary structures, enabling enzymes to catalyze reactions, provide support, transport substances, or signal between cells. In contrast, carbohydrates are made from sugar units, lipids are built from glycerol and fatty acids (not long chains of amino acids), and nucleic acids are polymers of nucleotides. Thus, the option describing molecules formed from long chains of amino acids is proteins.