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 Photosynthesis
  Cyclic Electron Flow and The Calvin Cycle
  Lecture by Glenn Wolkenfeld
 
 Thanks for joining  for Episode Two,
 Wher more ‘bout  waits for you.
  last saw how plant cells create, O¬¬2, ATP, and NADPH.
 Now we’ll  with a twist on the light reactions,
 Called cyclic  we’ll see how it happens.
 Then we will  how the Calvin Cycle makes carbohydrate.
 
  I, Cyclic Electron Flow)
 Non – cyclic flow is also called the “Z – scheme” Put Z on its  and see what I mean.
 Electrons  in energy then fall and rise again.
 Making ATP and  my friends.
 A variation on this is  flow.
 Which makes ATP, no NADPH or 
 Cyclic flow results from the Calvin Cycle’s 
 It uses less NADPH than 
 NADPH buildup has the repercussion,  inhibiting NADP+ reduction.
 ‘cause NADPH clogs  reductase.
  NADP+ from moving into place.
  electrons don’t go to NADP+.
 They’re clogged, stuck like a  pus.
  can they go from P700?
 Nature evolved them a place to 
  shunt pathway moves them to the ETC.
 I’m talking ‘bout  one in PS II tou see.
 These energized alectrons flow and release 
 Which as you know is used to synthesize 
 
  Part II: Calvin Cycle)
 Now it’s time to learn the cycle named  Calvin.
 Which results in the fixation  carbon.
 Consider that each carbon  your bones, blood and hair,
 Was once in a CO2 in the 
 The Calvin  has three parts.
 Fixation of carbon is  it starts.
 The molecules produced rae then 
 ‘cause reduction  the key thing that happens in part 2.
 Part 2 is the payoff  you will see.
 It  molecule G3P
 A reduced  with lots of energy.
 And a starting point for  the molecules that cells need.
 Part 3 sets up conditions for  cycle’s start.
  recreating what’s at the cycle’s heart.
 RuBP (Ribulose Bisphosphate), a five carbon molecule  seems to apparate.
 ‘Cause RuBP’s at  cycle’s start.
  reappears at the very last part.
 The role of RuBP at the start  end.
 Is why this is a  like the one named Krebs.
  cycle’s inputs are know to you: NADPH and ATP and CO2
 Fixation of carbon is catalyzed  RuBP Carboxylase Enzyme
 This enzyme’s nickname you should 
 Sounds like a cookie maker:  RUBISCO.
  enzyme so old it was already here,
 Before O2 accumulated  the air.
 The CO2 enters through leaf stoma,  through the leaf and arriving at the stroma.
 There RuBisCO grabs it in its  site, and squeezes it with RuBP tight.
 RuBP has carbons five, it has two phosphates, one on  side.
 When CO2 combines with RuBP it  a six carbon compound you won’t see.
 It instantly dissociates into  3 – phosphoglycerates,
 Each  three carbons and one phosphate.
 Each gets phosphorylated  bisphosohoglycerate.
  means that each receives aphosphate group from ATP.
  phospharylation, is followed by reduction.
 And you know there’s an enzyme with the 
  taking electrons and H from NADPH and adding them to to bisphosphoglycerate.
 Take off  phosphate for Glycealdehyde – Phosphate.
 A starting  for compounds like carbohydrates.
 
 (Part III: Calvin  conclusion)
 Glyceraldehyde- 3  phosphat, known as G3P,
 as a product cells  and I hope you see,
 how light  NADPH and ATP,
 are needed to fix CO2 and make  energy.
 And to complete  cycle we must now regenerate.
 The starting  of Calvin Cycle ribulose bisphosphate.
 The intermediates involved in  G3Ps,
  recombining them into RuBPs.
 Are  much for freshman biology.
 You can  the details when you get yors Ph. D.
 But know for now that to get 3 RuBPs from  G3Ps cost 3 ATPs!
 
 (Part IV: Conclusion)
 Now this journey ends whit  emphasis,
 On the reaction  photosynthesis.
 For over four billion years it’s been  food chains basis.
 In fossils from that era you can  the traces,
 Of tiny cells  prokaryotic form.
 Stromatolites  lived in waters warm.
 Through photosynthesis they transformed  planet,
 So aerobic life can live upon 
  so evolved sentient beings who can analyze,
 How photoautotrophs  photosynthesize.
 You could say that photosynthesis gave birth  codiyions for cons ciousness on Planet Earth!