molecule models of theobromine left, and caffeine right side by side. the red arrow highlights the only difference. white is

arrow atom atomic ball biochemistry biology black blue bond c7h8n4o2 c8h10n4o2 cacao caffein caffeine carbon chemistry chocolate coffein difference education elements geometry highlights hydrogen left medical methylxantine model models molecule nitrogen nutrition only organic oxygen pharmaceutical psychoactive purine red research right ring science side spheres stick stimulant structure theobromine visualization white xantheose