Which elements primarily compose carbohydrates?

Carbohydrates are organic molecules that primarily serve as a major source of energy for living organisms. Their structure is fundamentally composed of three key elements: carbon, hydrogen, and oxygen.

Carbon serves as the backbone of the carbohydrate structure, forming the core framework around which hydrogen and oxygen atoms are arranged. The general formula for many carbohydrates can be represented as Cn(H2O)m, which reflects their composition, indicating that for every carbon atom, there is typically a corresponding amount of water molecules (which include hydrogen and oxygen).

The presence of these three elements allows carbohydrates to perform a variety of biological roles, including energy storage (as in starch and glycogen), structural functions (as in cellulose in plants), and recognition processes (in glycoproteins and glycolipids). The specific ratio of hydrogen to oxygen in carbohydrates is ideally 2:1, aligning with the ratio found in water, further emphasizing the significance of these three elements in carbohydrate chemistry.

In contrast, the other options involve elements that do not compose carbohydrates or are found in entirely different biological molecules. For example, nitrogen, potassium, phosphorus, sulfur, and sodium are primarily associated with proteins, nucleic acids, or various cellular functions, rather than the fundamental structure of carbohydrates.