Which of the following occurs during the Calvin cycle? (A) carbon fixation (B) reduction of NADP+ (C) release of oxygen (D) generation of CO2

Video transcript

Hi everyone. Let's look at our next problem. It says identify the correct order of the three phases of the Calvin cycle. So we recall from our content videos that the Calvin cycle takes place in plants. And these are the light independent reactions sometimes called the dark reactions. So not the reactions that need sunlight to take place. And these are the reactions at the very beginning of this cycle where the plant is going to use carbon from carbon dioxide, it takes in and way down the line and the light reactions um use those carbons to store energy from the sun. So let's think about those three steps as we recall what we learned in our content videos. So in the first step we were called, we're starting here with carbon dioxide. So what we need to do with that carbon dioxide is fix it by incorporating it into other carbon molecules. So the first step that gives us a hint is carbon fixation. So if we look briefly at our answers here, we can see that we already can eliminate two of them. Choice A and choice d do not begin with carbon fixation. So, let's look at our first step here. Just remind ourselves In that first step, the carbon dioxide is combined with the Ru BP molecule. Let's just it's right here the review loose this phosphate. And in a two step process we're going to get two molecules of what's shortened to three P. G A or phosphor glycerol. It and these are three carbon molecules, whereas the rebellious by phosphate is a five carbon molecule. So we've got one carbon from the C. 025 from the R U. B. P. And we end up with six in the form of 23 carbon molecules. This then will go into the second step and the second step we start with that three P. G A phosphor glittery and we get a some phosphate added to it. Coming from A T. P molecules. We end up getting B P G A 13 biss boss focus rate which is reduced by N. A. D. P. H. And a reduction reaction with the end result that we end up with a product of G three P. Otherwise known as Glycerol to Hide three phosphate. So we look up here at our answers of B and C. Are two possibilities. Choice B has the second step of rebelo sbis phosphate regeneration. Choice C. Has the second step as glycerol died three phosphate synthesis. That is indeed what happened here. So we know that. Choice C. Must be correct. And we can go ahead and eliminate choice B. Just turn that into a line here. And then finally just to recall our third step here, We started with this G three p. It's combined with a T. P. And that will result in the regeneration of our ubp. We had We're gonna combine five of this G three P. Which is a three carbon molecule will generate three of the R. U. B. P molecules which is a five carbon molecule. So at the end we've regenerated our UBP. We also have a net game of one G three P molecule. This will go on down the line in the later reactions to generate glucose or other carbohydrates that the plant might need, such as cellulose or starch. So again we have our correct order for the three phases of the Calvin cycle choice C carbon fixation, glycerol three phosphate synthesis and then rebelo spice phosphate regeneration. Thanks for watching. See you in the next video.