in this video, we're going to begin our lesson on the cyclic versus non cyclic photo phosphor relation pathways that are possible during the light reactions. Now, the term photo fast for relation as its name implies, is going to be the phosphor relation of a. D. P. Into a teepee, creating energy for the cell. And it does this fast correlation by using solar energy or the energy of sunlight, which is where the photo route originates from. Since photo means light. Now there are actually two types of photo phosphor relation pathways that are possible during the light reactions. And so the first possibility for a photo fossil relation pathway is the non cyclic photo phosphor relation pathway. And the second possible pathway is the cyclic photo phosphor relation pathway. Now, as we move forward in our course, we're first going to talk about the non cyclic photo phosphor relation pathway because it's more consistent with what we've already talked about in some of our previous lesson videos. But then after we talk about the non cyclic photo phosphor relation pathway, then we'll move on to talk about the cyclic photo phosphor relation pathway and its own separate video. Now, what ends up determining which pathway the cell ends up using uh is going to be the cells specific requirement of reducing power in the form of N A. D ph as well as the cells specific requirement for a T. P. And so really we'll be able to talk more about this specific idea right here as we move forward in our course and talk about each of these pathways. And so that concludes our brief introduction to the cyclic and non cyclic photo fossil relation pathways. And I'll see you in our next lesson video to talk about the non cyclic photo fossil relation pathway. So I'll see you all there.

in this video, we're going to talk more about the non cyclic photo phosphor relation pathway. That is a possibility during the light reactions. And so really this non cyclic photo phosphor relation pathway is the normal light reactions that we've already covered in our previous lesson videos. And so when the cell requires the production of both A T. P and n A D ph uh then the cell is going to use the non cyclic photo phosphor relation pathway. And so the non cyclic photo phosphor relation pathway will produce both A T. P and N A. D ph. And this is going to be different when we talk about the cyclic photo phosphor relation pathway. And so this non cyclic photo fast correlation pathway, as its name implies with the non cyclic part is going to have a linear pathway or a linear path of electrons where the electrons are going to be passing through photo system to or PS two and photo system one in a linear fashion in order to make once again both A T P and N A D ph. And so the electrons will be taking a linear path. Uh And so once again, as I already stated, the non cyclic photo fast correlation pathway is pretty much the normal pathway of the light reactions as we already covered it in our previous lesson video. And so it is going to produce a T P and n A D P H. And that 80 P and n A D ph is going to be used in the Calvin cycle. And we'll talk more about the Calvin cycle later in our course. Now, if we take a look at our image down below, notice we're showing you an image of the non cyclic photo phosphor relation pathway. And so notice that the electrons represented and represented in blue here are going to be basically stripped away from the oxygen. And the electrons will go to photo system too. Okay, then the electrons go from photo system to through the electron transport chain back to photo system one. And then they will continue forward uh to uh N A D. P. H here. And so notice that the electrons are taking somewhat of a linear path. They start here and then the electrons are going in this direction as you see. And they end up on N A D ph. Okay. And so it is a non cyclic path that does not come back and cycle uh into a cyclic pathway. These electrons are taking a linear path. And so this is why it's called the non cyclic photo phosphor relation pathway. And so we know from our previous lesson videos that as the electrons are making their way through the electron transport chain, there is a large hydrogen ion gradient that's being built here within the Thilo coid space. And this hydrogen ion gradient can be used to create a T. P. And so the non cyclic photo phosphor relation pathway. Notice, as we mentioned up above in our text, generates both and a D P. H. And it also generates a T. P. So it generates both of them. And so the N A D P h A T. P. That are generated are going to be used in the Calvin cycle to power the Calvin cycle. And so this year concludes our brief introduction to the non cyclic photo phosphor relation pathway. And we'll be able to compare this to the cyclic photo fast correlation pathway as we move forward in our course. So I'll see you all in our next video.

in this video, we're going to introduce these cyclic photo fast correlation pathway. That is a possibility during the light reactions. And so when the cell only requires a T. P production, but it does not require any DPH production. The cell will actually use these cyclic photo phosphor relation pathway. Rather than using the non cyclic photo phosphor relation pathway, which recall from our previous lesson videos will produce both A T. P and n A D ph. And this is because the cyclic photo phosphor relation pathway, as its name implies, is going to include a cyclic path of electrons. And it's only going to be using photo system one to make a T. P. However, no N A D pH will be made during the cyclic photo fost correlation pathway. And so what happens during the cyclic photo fossil relation pathway is that high energy electrons from photo system one are actually going to be cycled back to the prior electron transport chain or E. T. C. In order to continue generating a proton motive force. And of course the proton motive force is going to be used to produce more 80 P. And so ultimately what we're saying is that the cyclic photo fast correlation pathway is going to have a cyclic path of electrons. It's only going to be using photo System one and it will only be making a T. P. It will not be making an A. D. Ph. And so if we take a look at our image down below notice we're showing you an image of the cyclic photo phosphor relation pathway. And so notice that the electrons uh you know, they will go from photo system to over to the normal photo system one here. However, once they reach photo system one notice that the electrons are taking a cyclic pathway Back to the previous electron transport chain. Okay, so not that they are transported through uh this exact uh path that you see here. However, the electrons and photo system one are eventually shipped back to a previous protein and the electron transport chain. And then the electron makes its way back to photo system one. And then it just continuously goes in this cyclic pathway. And so when the electrons are taking this cyclic pathway here, uh that cycles from photo system one back to the electron transport chain, back to photo system one and so on. Uh the electrons never are going to go to N A D P H as long as they continue in this cyclic photo fast correlation pathway. Um and so uh it is possible for the cell to switch from cyclic photo faster relation to the non cyclic photo fast correlation. But during the cyclic photo phosphor relation, what happens is there is going to be a continuous generation of a proton motive force. A continuous generation of a hydrogen ion gradient. And that hydrogen ion gradient can continue to make a T. P. And so only a T. P. Is going to be made during the cyclic photo phosphor relation pathway. And N A D ph will not be made. And so notice that we have this region and this region over here grayed out because they are not really used during the cyclic photo phosphor relation pathway. And the regions that are colorful, including this region right here in this region right here are colourful because these regions are being used by the cyclic photo fossil relation pathway. And so once again, what determines whether a cell will use the non cyclic pathway or the cyclic pathway is going to be the need for reducing power. How much any DPH does it need? If it does not need any DPH and it only needs a T. P. Then it's only going to perform the cyclic photo fossil relation pathway. However, if it does need N A. D. P. H and A T. P. It will use the non cyclic photo phosphor relation pathway. And so this year concludes our brief lesson to the cyclic photo fast correlation pathway. And we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video