In this video, we're going to introduce energy coupling. Energy coupling is basically when energy released by an exergonic reaction is used to power or drive an endergonic reaction that requires an energy input. Recall from our last lesson video that ATP hydrolysis is an exergonic reaction, and so ATP hydrolysis releases energy into the environment. ATP hydrolysis is usually what's going to be coupled to endergonic reactions because the released energy from ATP hydrolysis is used to provide the energy input that those endergonic reactions need to proceed. Let's take a look at our image down below to get a better feel for energy coupling.
Notice on the left-hand side over here, we're showing you this pizza, and that's because a lot of the energy that we get is from the foods that we end up eating. When we eat pizza, the pizza is going to have all different kinds of molecules in it. It's going to have carbohydrates, proteins, lipids, and more. Those molecules that are in the foods that we eat end up providing energy for our bodies. Our bodies are going to perform exergonic reactions to essentially break down the foods. You can see that here: we're showing you the reaction for exergonic reactions. They start with large food molecules and they break them down into smaller components, ultimately allowing for converting the energy that's in food into chemical energy in the form of ATP. This energy is going to be used to make ATP. Once ATP is made, the cell can perform ATP hydrolysis.
In this box, you can see the reactants that are needed for ATP hydrolysis to occur. Of course, they're going to need ATP for ATP hydrolysis to occur and also it's going to need water. ATP hydrolysis is going to be an exergonic reaction. When ATP is hydrolyzed, it is going to release a lot of energy as we can see here, being released, and also, it's going to end up creating a phosphate group as well as ADP. But this energy that is released is really important and this is where the energy coupling comes into play because ATP hydrolysis is an exergonic reaction and that exergonic reaction releases energy, and this energy is going to be used directly to provide the energy input that's needed for an endergonic reaction. Using smaller molecules to build larger ones when you're riding your bicycle, the energy that's being used is coming from ATP hydrolysis.
Now again, ATP hydrolysis is going to create ADP and a phosphate group, and these are really the reactants that are needed for ATP formation. You can see that ATP production energy that's going to be added into ADP is going to come directly from the energy in foods that we eat. Ultimately, with energy coupling, the movements that we have, the kinetic energy that we need to ride a bike is ultimately going to be derived directly by ATP hydrolysis and ATP hydrolysis has ATP whose energy comes directly from the foods that we eat, breaking down the foods that we eat. It's the foods that we eat that ultimately can be traced to providing the energy for our movements and muscle contractions. Exergonic reactions are used to power endergonic reactions, and this is the idea of energy coupling.
This here concludes our introduction to energy coupling and we'll be able to get some practice applying these concepts as we move forward in our course. I'll see you all in our next video.