Light independent reactions
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Light independent reactions

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Light independent reactions Light independent reactions Presentation Transcript

  • Light Independent Reactions The Calvin Cycle
  • Where did we leave off? Picture source: http://www.docstoc.com/docs/108591984/The-LightDependent-Reactions-of-Photosynthesis
  • Photo source: http://bioap.wikispaces.co m/Ch10+Collaboration Where are we going?
  • The Light Independent Reaction •AKA the DARK reactions •Does not necessarily take place in the dark but does not require light energy from photons to proceed •Requires ATP and NADPH from the light dependent reactions •Takes place in the Stroma •PURPOSE: to create a useful compound that the plant can convert to starch via GLUCOSE and other substances necessary for life Photo source: http://www.tutorvista.com/biology/chlor oplasts 6CO2 + 6H2O + Energy --> C6H12O6 + 6O2
  • Phase 1: Carbon Fixation •NOTE :To simplify the Calvin Cycle multiples of starting products are use to be able to create the whole amounts of end products. Therefore 3 CO2 molecules = 3 turns of the cycle •The Carbon of 3 molecules of CO2 is “fixed” with 3 molecules of the 5C RuBP. The enzyme Rubisco aids the reaction and O2 is released. •The 6C intermediate is very unstable and immediately breaks down into 6 3C molecules called 3phosphoglycerate +
  • Phase 2: Reduction •6 3-phosophoglycerate are reduced by ATP and combine with phosphate groups to create 6 molecules of the 3C 1,3-BPG •The ATP and NADPH used in reduction are the products of the Light Dependent Reactions •6 1,3-BPG are reduced by NADPH to create 6 molecules of 3C G3P
  • Let’s Talk about G3P • G3P is the product we have been aiming to make since the very beginning of photosynthesis! •G3P is a sugar intermediate which can be combined and rearranged in many ways to from bigger sugars such as glucose. •Glucose can then be transported to other areas of the plant and turned into sucrose, cellulose or stored as starch. • For every 6 G3Ps made only 1 is transported out of the stroma to be made into useful products. 5 stay in the Calvin cycle. •2 G3Ps are needed to make 1 molecule of glucose. Therefore the Calvin cycle must turn a total of 6 times per glucose.
  • Step 3: Regeneration •The 5 G3P left in the Cycle are further reduced by ATP to regenerate RuBP which restarts the cycle •The ATP in this reaction is a product from the Light Dependent Reactions
  • The Whole Picture For every 1 molecule of glucose produced: •The Calvin cycle spins 6 times • 6 CO2, 18 ATP and 12 NADPH are consumed • C6H12O6 and 6 O2 are produced along with 18 ADP and 12 NADP+ Photo Source: http://csmbio.csm.jmu.edu/bioweb/Bio480/Fall0 4/group7/plantexp/intro.htm