Download Friday Calvin Cycle How you will always remember… Rubisco

10/5/12 Friday Calvin Cycle And costs no ATP! 1.  Fixa5on –  Fixes CO2 to with RuBP to make 3-­‐phosphglycerate 2.  Reduc5on* –  3-­‐phosphoglycerate reduces to G3P –  G3P used to make sugars 3.  Regenera5on* –  G3P recombined to make RuBP Calvin Cycle Rubisco: an enzyme’s tale How you will always remember… Fig. 10.19 pg. 214 Rubisco Rubisco •  Ribulose-­‐1,5-­‐bisphosphate carboxylase/oxygenase •  Enzyme responsible for CO2 fixa5on •  Cube shaped (8 ac5ve sites) •  Slow, inefficient –  Only 3 reac5ons/sec –  O2 competes with CO2 •  Reac5ons with O2 results in a reac5on that undoes photosynthesis Wanted poster on a chloroplast: RuBisCO gene stolen from owner. If seen, please contact the green prokaryote hXp://www.growingpassion.org/2010/04/evolu5on-­‐of-­‐chloroplasts-­‐endosymbiosis.html CO2 O2 CO2 CO2 O2 CO2 CO2 O2 O2 –  Splits carbon and uses ATP CO2 O2 CO2 hXp://en.wikipedia.org/wiki/RuBisCO 1 10/5/12 What adapta5ons have come about to increase the efficiency or rubisco? Rubisco •  Maladap5ve! C4 Photosynthesis –  Reduces fitness •  Product of fixa5on •  How could this be? –  4-­‐carbon molecule –  Hypothesis: it was present before massive amounts of O2 were present in the atmosphere •  CO2 fixed in mesophyll •  Rubisco only in bundle sheath cells –  Predic5on: If rubisco had evoloved a`er O2 was present, then it would have developed a more specific binding site for CO2 to avoid compe55on with O2 hXp://en.wikipedia.org/wiki/RuBisCO C4 Photosynthesis hXp://plantphys.info/plant_physiology/c4cam.shtml FI. 10.23 PG. 217 What adapta5ons have come about to increase the efficiency or rubisco? CAM photosynthesis CAM photosynthesis Stoma must remain closed during the day to prevent water loss •  Carbon fixed only at night •  Adapta5on to dry condi5ons hXp://www.bestlandscapeideas.net/cactus/ hXp://www.sciencephoto.com/media/30376/enlarge –  4-­‐C organic acid –  Released as CO2 during the day 2 10/5/12 What adapta5ons have come about to increase the efficiency or rubisco? C4 Photosynthesis Ques5ons •  C4 and CAM photosynthesis are two ways to circumvent the inefficiencies of what enzyme? CAM photosynthesis • 
Product of fixa5on • 
Carbon fixed only at night • 
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CO2 fixed in mesophyll Rubisco only in bundle sheath cells • 
Adapta5on to dry condi5ons –  4-­‐carbon molecule –  Rubisco –  4-­‐C organic acid –  Released as CO2 during the day •  What makes Rubisco inefficient? Both work to increase concentra5on of CO2 for a more efficient Rubisco –  Slow reac5on speed –  Non-­‐specific binding of CO2 How to organisms get energy? •  Cells use a high energy molecule to fuel cellular processes Adenosine Triphosphate (ATP) Cellular Respira5on Glycolysis Krebs Cycle Electron Transport Chain phosphate ADP hXp://en.wikipedia.org/wiki/File:ATP_chemical_structure.png How to organisms get energy? Glycolysis hXp://homebrewsake.com/home/2010/04/25/koji-­‐what/glucose/ •  Glucose is ini5ally broken down in a series of steps called Glycolysis •  Occurs in the cytosol •  Yields a net 2 ATP, 2 NADH per glucose molecule •  Anaerobic (no oxygen) –  Used by aerobes and anaerobes hXp://staff.jccc.net/pdecell/cellresp/glycolysis.html •  10 step process to produce ATP, NADH, and pyruvate •  Glucose is the carbon and energy source used by most cells. 3 10/5/12 Krebs Cycle •  Occurs in the mitochondrial matrix –  In the cytosol of bacteria Figure 9.21 Do we have enough energy yet? Redox Reac5ons • 
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6 CO2 10 NADH 2 FADH2 4 ATP Where’s all the ATP? hXp://tha5sh.com/wp-­‐content/uploads/2012/07/confused-­‐face1.jpg •  Redox reac5ons are essen5al to produce more ATP in the Electron Transport Chain (ETC) hXp://archive.microbelibrary.org/ASMOnly/details.asp?id=400&Lang=English •  For each glucose molecule that is fully oxidized, the cell produces: –  indirectly via proton gradient hXp://www.eastchester.k12.ny.us/schools/hs/teachers/fishman/organelles.htm •  Produces 3 NADH, 1 FADH2, and 1 ATP per pyruvate •  Insert figure 9.21 from the book hXp://www.eastchester.k12.ny.us/schools/hs/teachers/fishman/organelles.htm •  A series of ~10 steps to oxidize pyruvate to 3CO2 The Electron Transport Chain Inter-­‐membrane proteins and cofactors help move protons created by redox reac5ons to the outside of the membrane •  Insert figure 9.24 from the book Figure 9.24 4 10/5/12 • 
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Proton Gradient Created ATP synthase takes advantage of gradient Produces ~ 26 ATP molecules per glucose Membrane-­‐bound process ATP Synthase + + + + Oxida5ve Phosphoryla5on •  Insert figure 9.26 from the book hXp://archive.microbelibrary.org/ASMOnly/details.asp?id=400&Lang=English hXp://mw.concord.org/modeler1.3/mirror/mechanics/undershotwaterwheel.html ATP Synthase Figure 9.26 Redox Reac5ons Krebs cycle Electron Transport Chain ADP ATP Figure 9.9 ATP Synthase 5