Carbohydrates contain which elements?

• A. C, H, N
• B. C, H, and O
• C. C, H, O, and P
• D. C, H, O, and S

Answer: (B)

Carbohydrates are built from carbon, hydrogen, and oxygen in a roughly 1:2:1 ratio, often represented by the formula CH2O in repeating units. A classic example is glucose, C6H12O6, which clearly shows this C:H:O makeup. Nitrogen shows up in proteins and nucleic acids, not in the basic carbohydrate structure. Phosphorus is a hallmark of nucleic acids and some energy carriers, and sulfur appears in certain amino acids. Some carbohydrates can be modified to include phosphate groups, but the core elements for carbohydrates are C, H, and O.