So here we have an example problem that wants us to fill in the blank here using one of these 5 potential answer options down below. The example problem says, there is an energy investment step needed to get glycolysis started requiring the use of 2ATP's. And once again we've got these 5 potential answer options down below. And so what we need to recall is that glycolysis has two phases, the energy investment phase and the energy harvest phase. The energy investment phase requires an investment of 2ATPs.

And so really that's what this example problem is getting at. In order for the energy investment step to occur, it requires the use of 2ATPs. And so the correct answer here is going to be answer option a. Now after the 2ATPs have been used, then the cell can transition to the second phase of glycolysis which is the energy harvest phase. And the energy harvest phase produces a total of 4ATPs and 2NADH.

And of those 4ATPs, because 2 of them got burnt, ultimately it's only a net of 2ATPs that are made. But once again in terms of the energy that needs to be invested, it's 2ATPs that need to be invested. So the correct answer to this example is answer option a, and that concludes this example. So I'll see you all in our next video.