system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is ATP used as energy in our bodies?

I've been taught that breaking ATP into ADP and a phosphate releases energy, but in chemistry I've learned that breaking bonds always requires energy, so I'm confused.
gpt
ATP is adenosine triphosphate. It's an adenosine molecule with 3 phosphate groups attached. The phosphate to phosphate bond has a lot of energy stored in it. ATP then goes to various enzymes in your cells. An enzyme called a kinase helps remove a phosphate group off of ATP and attach it to another enzyme. Generally speaking, when that enzyme has a phosphate group attached, it's activated and can do important things in your body. For example, some enzymes break down glucose to make more energy. Others pump sodium out of your cell and potassium in.

The reason why ATP gives off energy is because ATP hydrolysis has a negative Gibbs free energy. This means that ATP is not in the most stable form. It wants to get rid of that phosphate group and the energy associated with it. If a reaction has a positive Gibbs free energy, it needs energy in order to proceed. 

It's sort of like if you have a wagon on a hill. If you are at the top of the hill, you have a lot of potential energy. If you just give the wagon a small push, it will fly down the hill. But if you are at the bottom of the hill, you need to give it a bunch of your energy by rolling it to the top of the hill first.

There is one more useful detail here. The wagon didn't start flying down the hill until you gave it a little push. Even though it "wanted" to fly down the hill, it needed a little bit of extra energy to start before it could let gravity take over. In the same way, most chemical reactions need a bit of activation energy before they start to proceed. ATP works the same way. It needs a tiny amount of activation energy before it can give off its energy. Enzymes lower the activation energy needed for ATP to transfer a phosphate group. They don't affect the Gibbs free energy at all, but they make the activation energy needed  much lower so the reaction can proceed more easily. Generally speaking, your body regulates these enzymes so that it uses more ATP when useful and stops using ATP when useful.