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 Photosynthesis : part A -  Light Reactions
 Amusical Lecture by Glenn 
 
  music Lecture by Glenn Wolkenfeld
 Boys  girls tell me what you think of this,
 Time  a lesson ‘bout photosynthesis
 Cells use light to  water carbon dioxide.
 Gonna see electrons  for a wild ride.
  sugar, making sweet O¬2.
  why should photosynthesis matter to you?
  on your table.
 O2 rich atmosphere.
 Without photosynthesis  simple wouldn’d be here.
 
 ( Part I, The Big 
 Photosynthesis is a  reaction.
 Powered by  using enzymatic action.
  oxidized, CO2’s re duced
 The  that results you drink in orange juice.
  overall reaction has two phases.
 First is the light reactions which  as its basis.
 Light powered production  ATP.
  is the by – product and you will see.
 Production of electron  NADPH
 Which provides  power needed in the second phase
  NADPH, during phase 2
 Provides what’s  for reducing CO2
 NADPH  made by a reduction of NADP+, whose function
 Is to  electrons and pick up H,
 Gaining energy  making NADPH.
 Phase 2 is the Calvin Cycle  carbohydrate,
 Like sugar and starches and  on your lunch plate.
 It’s how  make food animals eat.
  it’s so sweet!
 
 (Part II: Chloroplasts, Thylakoids,  and Chlorophyll)
 In a lesf there’s  tissue
 And cells  chloroplasts key to the issue.
 Chloroplasts are almost like cells  every way,
 With their own  and their own DNA.
 They even  themselves, splitting into half.
 A clue for this organelle’s  past.
 This theory has  name endosymbiosis,
 Developed  the 60s by Lynn Margulis.
 Inside the chloroplast  the fluid stroma.
  true in Tokyo.
 It’s  in Roma.
 Stroma syrrounds  thylakoids.
 Each one has  hollow space inside.
 The thylakoid’s membrane is loaded with 
 ‘Cause it’s  light reactions’ scene.
 It’s all about  light for powering electrons,
 All  grabbing the power in photons.
 The photons needed are are those from 
 Which has the  to make the world bright.
 The highest frequency  we can see,
 Is violet  with wavelength 380.
 380  sounds small,
 But next  gamma rays it’s rather tall.
 Red light  at 750.
 Isn’t the  spectrum nifty?
 Photons are  of light energy,
 Both a wave and a  you see.
 Phootins get  by pigments.
 It’s real, it’s true, it  no figment!
 Most important are  chlorophylls.
 Orange carotenoids,  yellow xanthophylls.
  they absorb light, mostly red and blue.
 The green is  absorbed it reflects back to you.
 In  see the porphyrin ring.
  the magnesium, which makes you want to sing,
  metal with valence two.
 You’ll  those electrons rocketing through.
 Notice the tail,  hydrocarbon chain.
 Which anchors chlorophyll into the  membrane.
 A molecule with style, so 
  the thylakoid it makes electricity!
 
 ( Part III)
 Englemann  us the action spectrum.
 Used a  to break the sun’s
 Light into  frequencies.
 Shone it on spirogyra, filamentous 
 The  algae make will stimulate bacteria.
 Which will grow  any oxygen – rich area.
 Bacteria loved it over blue and 
 But  grew over green, they might as well be dead!
 The line of growth  a refection, of photosynthesis’ action spectrum.
 Note  won’t match, exactly,
  absorption spectra of chlorophyll a or b.
  the cartenoids and xanthophylls we’ve met,
 Absorb light frequencies the  can’t get.
 And  the thylakoid they all cooperate,
  using light to synthesize carbohydrate.
 Consider chlorophyll  isolation,
 Shine some light upon  (call it photoexcitation)
  valence electrons in magnessium
 Jump to an excited state, it’s  fun!
 But once up at that level, they  only fall.
 Back to where they started, like  bouncing ball.
 These falling alectrons,  energy,
 Fluorescing as red  as you can see.
 But in thylakoids, chlorophyll’s  alone,
 Instesd a  is chlorophyll’s home.
 The photosystem’s parts can  photons,
  use their energy to move electrons.
 The system’s  complex does the first capture,
 Changing  anergy into electron rapture.
 The energized electrons bounce like  ball,
 At  reaction center, they jump but do not fall.
 A primary electron acceotor grabs them  on top,
 And  them with a force reaction center cannot stop.
 To this  reaction center we’ll return,
 But the details  electron flow it now is time to learn.
 
 ( Part IV) ATP Synthesis in Non  Cyclic Electron Flow.
  -  cycle flow is the main pathway.
 Much  relates to the way
  II precedes photosystem I.
 It’s a  to memorize, just get it done!
 PS II’s  captures a photon,
  a flow of electrons.
 All  the world, even n Haiti,
 They flow  reaction center P680.
 There electrons do not 
  acceptor passes them over.
  the electron transport chain,
 In  thylakoid membrane.
 This chain’s  a bucket brigade.
 Each molecule has  similar trade.
  take energized electrons,
 And use  energy for pumping protons.
 From  to the thylakoid space.
 Packing protons  that place.
 This makes  gradient across the thylkoid membrane
  protons want “out” or they’ll go insane.
 But  protons can’t permeate.
 The membrane won’t allow 
 There’s only one port through  they travel.
 It’s the  Synthase channel.
 The  tells you this is an enzyme.
 Which makes ATP  the time.
 It  binding sites for ADP and Pi,
 And channels for  protons whose knetic energy.
 Changes the  sites’ conformation.
 Fusing  with Pi which for your information.
 Is how  make ATP.
 Life’s key  of energy.
  respiration this might feel familiar.
 ATP  made this way in mitochondria.
 Chemiosomosis is  name
 ATP  is the game.
 
 ( Part V: NADPH  in Non – Cyclic Elecron Flow)
 Back to our electons moved by the 
 Flowing from Photosystem II to System 
 They get  PS I lke a used up battery.
 The transport chain  up their energy.
  when light hits PS I’s antenna
 Electrons boune to reaction 
 This one’s P700,
  wavelength makes electrons go!
 PS T’s electron  grabs them away,
  P700 in an oxidized way.
 And P700 with its oxidized blues accepts the alectrons from  II.
 Bak to  from PS I.
 It now gose for a ride, having its own 
 But powering proton pumps ain’t its 
 It travels to  reductase.
  enzyme plant cells count upon.
 To  some H and electrons.
 To NADP+  gets reduced.
 It’s how  get produced.
 
 (Part VI: Oxygen Production  Non – Cycli Electron Flow)
 The by – product of  light reactions
 Is  here’s how it happens.
 Back PS II, it came to 
  P680 got oxidized
 To replace lost electrons P680 
 Electrons  water which dissociates.
 Into one oxygen  protons two,
 The single O  meet anoher forming O2.
 These protons are formed in the  space.
 Increasing proton concentration in that 
 So we see a  effect of water’s oxidation.
 Is enhancement  ATP creation.