Adenine is one of the four nitrogenous bases while Ribose is one of the two sugars (carbohydrates) that make up a nucleotide. Adenine is structurally composed of 5 carbon atoms, 5 hydrogen atoms and 5 nitrogen atoms to form the chemical formula C5H5N5 whereas ribose is structurally composed of five carbon atoms, ten hydrogen atoms, and five oxygen atoms to form the chemical formula; C5H10O5.
Based on the above explanation, it is evident that the element present in Adenine but not in Ribose is NITROGEN. Nitrogen is a major constituent of all nitrogenous bases (Adenine, Guanine, Cytosine and Thymine (Uracil).
