Question

which element is always present in proteins but not in carbohydrates or lipids? sulfur nitrogen phosphorus calcium

Explanation:

Carbohydrates and lipids are composed mainly of carbon, hydrogen, and oxygen. Proteins are made up of amino - acids, and nitrogen is a key component of amino - acids. Sulfur can be present in some proteins but not always, phosphorus is not a main component of basic protein structure, and calcium is not a component of proteins.

Answer:

Nitrogen