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Photosynthesis_from Sciencefreaks

Added Oct 29, 2012 •

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welcome to the second annual lecture for chapter 7 here we will finish the process of photosynthesis with the dark reaction the second phase of fun when does the dark reaction because it does not need light to occur that doesn't mean it can't occur during the day just let it doesn't require light it is also known as the open cycle sometimes even the calvin-benson cycle after both scientists who discovered it so you do need to know those two terms are interchangeable Calvin cycle and dark you also need to keep the citric acid cycle attached to cellular respiration and the Calvin cycle dark reaction attached to photosynthesis in your brain don't mix them up  notice that the dark reaction occurs in the stroma of the chloroplast it use the nadph and ATP produced by wake reaction and the CO2 that is brought into the leaf through the stomata to make glucose but take a closer look  what are three steps sun cycle the first of carbon dioxide fixation or carbon dioxide is attached to a 5 carbon Rivals is phosphate molecule to make a fixed carbon intermediate module the six carbon intermediate molecule immediately splits into two three carbon 3pg molecules this process is catalyzed by the enzyme Rupp carboxylase also known as rubisco here's a quick side note there's going to be a lot of acronyms come up with some way to keep them straight I'm not sure how to do it other than just memorizing them there are also several different acronyms used for the same molecule and I'm if you both so you can decide which is easiest to remember but I wouldn't know both pairs for each molecule I would choose one set of acronyms for each molecule to memorize rubp is ribulose bisphosphate 3pg molecule is also known as a module interchangeable acronyms and this is just the first step of the Calvin cycle the second step is Carbondale reduction through a series of changes 3pg is converted to BPG which is then converted to g3p how do you say energy in ATP molecule and the electrons and hydrogen carried by the nadph molecules remember when we're both these molecules came that's the light reaction in the thylakoid membranes what are those other acronyms PGA changes to PJP which changes to PGA now or pig out so you can either memorize 3pg BPG and g3p or you can remind PGA PGA p p Gap help cow  the last step of the Calvin cycle is regenerating rubp to start the cycle over again this requires and key from ATP remember either converting to our ubp or Pal the rub so let's put all three steps together as we go through I'm going to highlight the number of molecules moving through the process notice to read carbon dioxide Perfect Two Three rubp molecules which break into six 3pg molecules or six PGA molecules ATP and nadph are used to convert the six through PG's into six g3p molecules or 6p gal molecules now I've g3p molecules or 5p gal molecules are used to regenerate the three rubp molecules that start the process all over using ATP to do so where does one of those g3p or pgal molecule go at least cycle entropy modules or 2p gal molecules join together to form glucose and that's the whole point of the cycle so just like the Krebs cycle and cellular respiration turn up to a card twice the dark reaction in photosynthesis has to occur twice to make one molecule of glucose now a lot of enzymes are used during the fight forever the only one you need to know is your VSCO now let's watch a video that will animate this process for us open cycle is a series of reactions that results in conversion of carbon dioxide into the organic molecules needed to build new cells it occur reap in the stroma which is the area of the chloroplast surrounding the thylakoid membrane  During the Calvin cycle carbon dioxide CO2 is added to a five carbon molecule called rubp the resulting six carbon molecule is unstable and quickly splits two to three carbon molecules called three phosphoglycerate using energy from ATP and reducing power from adph which are products of the light reactions the pair of 3 phosphoglycerate move through a series of reactions and are converted into two molecules glyceraldehyde 3 phosphate when several of these glyceraldehyde 3 phosphate molecules have been produced some combined to make glucose While others are used in the Calvin cycle  to generate an entire new glucose molecule that still has to turn several times because each turn of the cycle as only one carbon atom from each molecule of carbon dioxide congratulations Yuri end of the second to the electrical chapter 7 that didn't take nearly as long as the light reaction but hopefully now you're able to put it all together see you on the next one

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