MCB 181 1st Edition Lecture 18Outline of Previous Lecture I. OverviewII. ChloroplastsIII. Clicker QuestionsOutline of Current Lecture I. PhotophosphorylationII. Light Independent Reactions Current LectureI. Photophosphorylationa. Production of ATP molecules using the energy released as light-excited electrons flowthrough an electron transport chain during photosynthesisb. Involves the generation of a proton-motive force during electron transport and is used to drive ATP synthesisII. Light Independent Reactions (the Calvin Cycle)a. Calvin Cycle fixes carbonb. The Three Phases of the Calvin Cyclei. Fixation – CO2 reacts with RuBP1. This fixes carbon into a more complex molecule2. Carbon fixation is the addition of a carbon dioxide to an organic compoundii. Reduction – 3-phosphoglycerate is phosphorylated by ATP and then reduced by an electron from NADP, producing gluceraldehyde-3-phosphate (G3P)1. Some of the G3P leave the cycle to manufacture glucose and fructoseiii. Regeneration Phase – the rest of the G3P continues in the cycle and as a result, RuBP is regeneratedc. Photorespirationi. Rubisco is a carboxylase which means that it adds CO2 to RuBP however, it can also be an oxygenase, adding O2 to RuBP1. These two reactions compete with each other2. When RuBP reacts with O2, it cannot react with CO2, which reduces the rate of CO2 fixationd. C4 vs CAM plantsi. Basically C4 plants are known for storing their CO2 in one cell and with CAM plants, they store CO2 at night to minimize the amount of water leaving the
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