An investigator exposes chloroplasts to 700-nm photons and observes low O2 production, but high ATP production. Which of the following best explains this observation? a. The electrons from water are directly transferred to NADP+, which is used to generate ATP. b. Photosystem II is not splitting water, and the ATP is being produced by cycling electrons via photosystem I. c. The O2 is being converted to water as a terminal electron acceptor in the production of ATP. d. Electron transport has stopped and ATP is being produced by the Calvin cycle.

Video transcript

Hi everyone. Here's our next problem. It says what will happen when a chloroplast has a higher rate of cyclic photo phosphor relation than non cyclic photo phosphor relation. Well, let's recall from our content videos what cyclic versus non cyclic photo phosphor relation is. Well, this refers to the light reactions in which in the presence of light a phosphate is added to a to A D. P. Producing a T. P. So you have light energy absorbed phosphate added to ADP to produce a T. P. The difference is that in cyclic photo phosphor elation. We recycle the electrons used in the electron transport chain over here. So you have the electron excited by the light energy gets passed on to the electronic sectors of the electron transport chain. When it gets the end of that chain, that electron is transferred back to the chlorophyll at the beginning of that whole series of reactions. So electrons returned to the chlorophyll. So you can see we have a continuous cycle. The electrons are not passed on to electronic sectors. So as a result we generate a T. P. Because you still have the electron transport chain causing the production of a T. P. But we do not generate N. A. D. P. H. Because N A. D. P is an electronic sector that accepts can accept electrons from electron transport chain in non cyclic photo phosphor elation. The electrons are transferred to an electronic sector at the end of the electron transport chain. So this process generates a T. P. And N A. D. P. H. And in addition a non cyclic foot of hospital relation. Water is needed continuously. Um because atoll icis the breaking of the bonds and water. The water molecule is what's needed in this reaction. That produces N A V. P. H. So let's look at our answer choices again. Looking for what happens when you have a higher rate of the cyclic photo phosphor elation. So choice A says morph atoll icis takes place splitting water and generating more oxygen. Um that is not correct because water is needed for the non cyclic process. So high rate of cyclic possible relation is not going to call for more water. Choice B says more. A. T. P. Is being produced by cycling electrons versus photo system via photo system one only. Um that is correct. A T. P. Is reproduced by cycling electrons. Um That's something that wasn't on our little chart here. Cyclic photo phosphor relation uses photo system one only, whereas non cyclic uses photo systems one and two. So choice B is correct. Photo System one is the only one being used and A T. P. Is being produced by cycling electrons as opposed to passing them along to the electronic sectors. Choice C says more N A D. P H is produced by N ADP reductase enzyme. Well, that's not correct. As we discussed. N A D P H is not produced in cyclic photo phosphor relation only in a non cyclic version. So choice seeing not our correct answer. And finally, choice D. More glucose molecules are produced by the Calvin cycle. Well, Calvin cycle comes later after photo phosphor relation as part of the dark reactions. So choice D is not our answer here, because we're talking about before the Calvin cycle even takes place. Will that will be it for this video? We'll see you in the next video.