Let me share with you a comparison between purines and pyramidines.
| Aspect | Purines | Pyrimidines |
| Structure | Double-ring structure, containing a six-membered ring and a five-membered ring | Single six-membered ring structure |
| Names | · Adenine (A) · Guanine (G) | · Cytosine (C) · Thymine (T) · Uracil (U) |
| Molecular formula | C5H4N4 | C4H4N2 Cytosine and Thymine C4H4N2O2 for Uracil |
| Hydrogen Bonding Patterns | Adenine (A) forms two hydrogen bonds with Thymine (T) in DNA or Uracil (U) in RNA | Guanine (G) forms three hydrogen bonds with Cytosine (C) |
| Base Pairing Stability | Generally more stable due to the additional hydrogen bond in base pairs | Generally less stable due to fewer hydrogen bonds in base pairs |
| Cofactors in Metabolism | Involved in the structure of coenzymes like NAD and ATP | Not typically involved as cofactors in metabolism |