[ongzz (OP)]

Why do we need to do the De Novo synthesis of ATP, when we already have oxidative phosphorylation? Oxidative phosphorylation is a useful way to produce ATP in a large scale. Why it is still necessary to build ATP via De Novo synthesis pathway? Why we can't purely rely on the ATP produced by oxidative phosphorylation?

[Bored chemist]

How much ATP does a baby need?
How much do you need?

Also, adenine is used for other things.