cellular respiration questions?

The question is: How do living organisms drive endergonic processes? (from the nelson 12 textbook)

I was just wondering if somebody could look over my answer and tell me whats missing or wrong?

I put that:
living organisms use ATP as a source of energy that is needed to drive endergonic reactions. The ATP molecule is a highly unstable molecule due to its three highly negative phosphate groups. As the terminal phoaphate is released from the ATP, energy is released which is then used to attach that phosphate onto a reactant that is to undergo the endergonic reaction. Once the phosphate is attached to the reactant, the reactant is now also highly unstable and has reached the transition state and will readily react spontaneously.