Which elements are common to both carbohydrates and fats?

• A. Nitrogen
• B. C, H, O
• C. Phosphorus
• D. Sulfur

Answer: (B)

Both carbohydrates and fats are built from the same basic elements: carbon, hydrogen and oxygen. Carbohydrates often show this with the (CH2O)n pattern, reflecting equal parts carbon and water. Fats are mainly carbon and hydrogen with some oxygen in the ester linkages of their fatty acids, so their fundamental makeup is still C, H, and O. Nitrogen is a hallmark of proteins and nucleic acids, not of the basic structures of these two macronutrients. Phosphorus and sulfur appear in specific related molecules (like phospholipids or certain vitamins and proteins), but not as universal components of the everyday structures of carbohydrates and fats. So the common elements to both are carbon, hydrogen and oxygen.