Which element is a distinguishing component of proteins that is generally not found in carbohydrates or lipids?

• A. Chlorine (Cl), an ion involved in osmotic balance and gastric HCl production but not a core elemental component of proteins.
• B. Phosphorus (P), often abundant in nucleic acids and energy transfer molecules but not a defining element of proteins.
• C. Nitrogen (N).
• D. Calcium (Ca), a mineral commonly associated with bone tissue rather than the basic composition of protein macromolecules.

Answer: (C)