Question: how do atp and adp differ in the number of ribose molecules?
Answer: ATP (Adenosine TriPhosphate) has three (“tri”) phosphate groups — HPO, commonly referred to as P— bound to a pentose sugar (ribose), which is attached to a purine base (adenine). ADP (Adenosine DiPhosphate) has the same structure as ATP, except it has two (“di”) phosphate groups bound to the sugar/adenine base.