Photophosphorylation 3 - Video Tutorials & Practice Problems
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Photophosphorylation 3
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Our story here actually begins with photo system, too, which might seem odd, but the naming convention has to do with the fact that Photo System one was discovered before photo system to so photo system, too, has a chlorophyll in its reaction center called Pete 6 80. And that basically means this chlorophyll absorbs light at 680 nanometers really well. And what's going to happen in photo system, too, is when it loses electrons, thio, theological tronic sectors from the reaction center. It's going to split water to replace those lost electrons, so it's not going to have them returned by the electron carriers like we mentioned before. Um, and that's because photo system to, uh, photo system, whose main job is to provide the electrons for what's called non cyclic or linear electron flow. So it's going to split water into electrons. You, me do like this. We're breaking up water, and we're turning it into electrons, and we are giving off oxygen and protons as a result of this. Just to be clear, the membranes not drawn in here but there is, you know, a membrane here, and this side is the Lumen of the file a coid and this side is the Strom A And what's important to remember is this cytochrome complex. Its job is to pump protons through to this side. So the fact that the splitting of water also generates protons means that the splitting of water is even helping to build that proton radiant. Now, uh, the splitting of water actually uses mangga knees in the protein, and it actually uses all five Redox states of mangga knees. So pretty cool. Just one of those rare instances where mangga knees is used in biology. And after the electrons leave photo system to they go thio this cytochrome complex which is cytochrome B six f it contains, he seems iron, sulfur proteins, beta care teen, and it acts as a proton pump that receives electrons from this electron carrier right here called plast. Oh, we know abbreviated peak you as you see and it's going thio act as a proton pump. Just clear up this space and bring through protons. Now, uh, the electrons will move through this cytochrome complex first to the cytochrome B six portion than to the cytochrome F portion and finally to a copper in plastic sign in right here. Plaice, toe sign and and plastics Sion in is going to deliver its electrons to you. Photo system one. So here is photo system two. And here we have photo system one. All right. Now, the reaction center of photo system one contains chlorophyll P 700 right? So I'm sure you can guess what that name significance is. It absorbs light best at 700 nanometers. And what's important to realize about all of this is that, uh, the original wavelength we started at was 6 80. And remember, the shorter the wavelength, the higher energy, the photon we're talking about, right? So 6. 80. And now we're at 700. So slightly lower wavelength, slightly less energy from these electrons, so to speak. You know, that is in essence, what in part with this figure is trying to show Is the energy changes along this? If you imagine, like, a y axis along here, right, this is showing the energy changes of the electrons roughly as they progress through this system. So when they get to the reaction center of photo system one, remember that photo system one is also absorbing sunlight, and it is needing Thio replace the electrons it loses to the Elektronik sectors. So that is what photo system twos, electrons do they come in, they replace the electrons that photo system one loses and, um, travel from the reaction center to the Elektronik sectors. Thio this model or this electron carrier paradox in which will, uh, either bring them thio n a d p plus reductase right, which is going to ultimately form N a. D. Ph by reducing N a. D p plus or or paradox in can also bring these electrons back to the cytochrome complex and drop them off there where they'll move through the complex again pumping mawr hydrogen is through and they'll be picked up by plastic sign in and delivered back to photo system one. So that is the difference between cyclic and non cyclic electron flow essentially in cyclic electron flow. We basically have this cycle of from photo system 12 paradox in to the cytochrome complex to plasticine and then back to photo system one again, and this cannot generate any n a d p plus Write it on. Lee generates. This is important. This Onley generates a ah uh a Proton Motive Force. So it on Lee leads to the generation of ATP. So going to write that in Onley produces ATP on Lee produces ATP whereas non cyclic electron flow produces ATP Me jump out of the way here produces ATP and in a d p h. All right, so the ultimate purpose of creating this proton greedy int just like in oxidative phosphor relation is to power ATP synthesis. So here is kind of an overview of what's going on in this whole process. We have photo system to photo system one and electron flow from photo system to goes this way. Right. And we can also have linear electron flow which will simply cycle. I'm sorry. Cyclic electron flow. I said linear electron flow cyclic electron flow which will cycle like that. And this builds a proton, Grady, in which you can see here we have a Proton Motive Force right there and that is going to power ATP synthesis in. Just to be clear, this is Lumen. This is this Troma, and this is the Strama, right? So you know. All right, we're just seeing a cross section. But this will. You know, this membrane will you know, have ah edges to it, so to speak. This is ah contained area in the Lumen with the strom A surrounding it. And this whole process is called photo phosphor relation. And you can see that it's very similar to oxidative foster correlation. The difference being that sunlight energy rather than Thea oxidation of nutrients is providing the energy the source of energy ultimately for ATP synthesis. So this is sort of the other big a teepee generation process. In addition, Thio oxidative phosphor relation. Now that's all I have in terms off, uh, concept videos for this review. So let's turn over to practice problems.