Cytosine, guanine, thymine, and adenine are collectively referred to as nitrogenous bases. These are not phosphates. The cytosine, guanine, thymine, and adenine are the four different types of nitrogenous bases. These nitrogenous bases are present in the deoxyribonucleotides. Cytosine and thymine are smaller in structure and have single ring structures. These are collectively called pyrimidines. On the other hand, adenine and guanine are the larger nitrogenous bases each with double ring structures. They are collectively called purines
