Which of the following is NOT one of the key classes of organic compounds?

Vitamins are organic compounds that are essential for various metabolic processes in living organisms, but they are not considered one of the primary classes of organic macromolecules fundamental to biological structure and function. The key classes of organic compounds include proteins, nucleic acids, carbohydrates, and lipids, all of which play critical roles in cell structure and function.

Proteins are made up of amino acids and are crucial for numerous cellular processes, including catalysis (as enzymes), signaling, structural support, and transportation. Nucleic acids, such as DNA and RNA, are vital for genetic information storage and transfer. Carbohydrates serve as energy sources and structural components of cells. While vitamins are indeed important for health and play supporting roles in many biological functions, they are classified separately from these major macromolecular groups.

Understanding this distinction helps clarify the foundational roles these organic compounds play in biological systems.