Describe the three phases of the Calvin cycle and how the product...

Question

Describe the three phases of the Calvin cycle and how the products of the light-capturing reactions participate in this process.

Accepted Answer

Welcome back, Here's our next problem. It says the Calvin cycle includes three main phases namely carbon fixation, reduction and regeneration of the carbon. Except er which one of the following options correctly describes all these three phases. So let's recall from our content video kind of the overview of the Calvin cycle. And just to help out, I'm going to put up a little, there's not a lot of space so it's kind of tiny. But again we just want to kind of trigger our memory of these basic steps. So our first step is carbon fixation. Starting with that atmospheric carbon dioxide, we have a brief six carbon intermediate that splits into carbon molecules of three P G. A the second step or second stage excuse me, reduction. Um When we have electrons being donated by any DPH an electron donor to reduce the three P. G. A. The acid into a sugar G three P. And that step also utilizes A. T. P. Then we have one molecule of the G three P. Going off to make glucose. You need two of them to make the six carbon glucose. The other five getting utilized in the third stage regeneration, A T. P. Is consumed. And those five G three P are used to regenerate the five carbon R. U. B. P. That is used to fix C. 02 back again to the first stage carbon fixation. So with that overview back in our minds, let's look at our answer choices choice A says A T. P. Is utilized in all phases. Well, when we look at our little diagram and recall this A. T. P. Is not used in carbon fixation, carbon fixation, we just have to go to combining with our UBp catalyzed by the enzyme rue Biscoe. So eight Ep is utilized in reduction and regeneration but not carbon fixation. So Choice A. Is incorrect. Choice B says A T. P. Is utilized in both reduction and regeneration phases while any DPH is utilizing the reduction phase only. So as we look at our diagram, so again, a teepee in reduction and regeneration and 80 ph and reduction only. We already discussed that yes, A T P is utilized just in reduction and regeneration N A D. P. H. Over here, just in that reduction phase. And that makes sense because again, we know reduction involves we need we need to donate electrons. The thing we're reducing and any DPH is an electron donor. So that can help us remember that. So Choice B is correct. We're gonna go ahead and highlight that. But let's go through our other two choices. Just to be thorough here. Choice C says carbon dioxide is utilized only during the reduction phase. Well, that's incorrect. Carbon dioxide is in the carbon fixation phase. And we can help remember that when we think of C. 02, it's floating around in the atmosphere and we need to fix it into a molecule in the plant. So um that can help us remember that. So Choice C. Not correct. And finally, choice D. The reduction phase is the first phase of the Calvin cycle. Well, again, we can help remember if we think of plants taking carbon dioxide, give off oxygen taking in that CO two has to be the first phase, so carbon fixation of the first phase, not reduction. So Choice D. Also incorrect. So again, which is the correct statement here. Choice B a T P is utilized in both the reduction and regeneration phases, while any DPH is utilized in the reduction phase only see you in the next video.

Describe the three phases of the Calvin cycle and how the products of the light-capturing reactions participate in this process.

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