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Photosynthesis:
             Life from Light and Air




AP Biology                             2008-2009
Energy needs of life
    All life needs a constant input of energy
            __________________________
          get their energy from “eating others”
consumers  eat food = other organisms = organic molecules
          make energy through respiration
            __________________________
              produce their own energy (from “self”)
              convert energy of sunlight
producers
              build organic molecules (CHO) from CO2
              make energy & synthesize sugars through
AP Biology    photosynthesis
How are they connected?
    Heterotrophs
    making energy & organic molecules from ingesting organic molecules

     glucose + oxygen → carbon + water + energy
                        dioxide
      C6H12O6 +      6O2     → 6CO2 + 6H2O + ATP
             oxidation = exergonic
    Autotrophs                                                   Where’s
    making energy & organic molecules from light energy          the ATP?

     carbon + water + energy → glucose + oxygen
     dioxide
       6CO2 + 6H2O + light → C6H12O6 + 6O2
                    energy
AP Biology     reduction = endergonic
What does it mean to be a plant
    Need to…
            collect light energy                  ATP
              transform it into chemical energy
            store light energy
              in a stable form to be moved around
glucose        the plant or stored
            need to get building block atoms CO
             from the environment               2
                                                  H 2O
              C,H,O,N,P,K,S,Mg
                                                        N
            produce all organic molecules             K P
             needed for growth                          …
              carbohydrates, proteins, lipids, nucleic acids
AP Biology
Plant structure
    Obtaining raw materials
            __________
              _______________________
            __________
              _______________________
            __________
              _______________________
            __________
              N, P, K, S, Mg, Fe…
              _______________________

AP Biology
stomate



   ______________
AP ______________
   Biology
Chloroplasts
                        cross section      absorb
leaves                     of leaf
                                        sunlight & CO2
                                                    CO2


        chloroplasts
        in plant cell



                           chloroplasts
 chloroplast                  contain
                            chlorophyll       make
 AP Biology                               energy & sugar
chloroplast
                                                         H+ H +H + H++
                                                               +  +

   Plant structure                                   H H
                                                       +   +
                                                             + H H H
                                             ATP        H+ H
                                                           thylakoid
    Chloroplasts
            _________________
            _________________         outer membrane              inner membrane
              fluid-filled interior
            _________________
                             stroma
            _________________
    Thylakoid membrane
       contains                                    thylakoid
                                                               granum
            chlorophyll molecules
            electron transport chain
            ATP synthase
              H+ gradient built up within
               thylakoid sac
AP Biology
Photosynthesis
 ____________________
    _________________________
    _________________________

        convert solar energy to chemical energy
        ATP & NADPH
                                        It’s not the
 ____________________                 Dark Reactions!
    _________________________
    _________________________

        uses chemical energy (ATP & NADPH) to
         reduce CO2 & synthesize C6H12O6
 AP Biology
chloroplast                          thylakoid
                                                                    H+ H+ +
                                                            H+ H+H + H+H+H +
                                                                     +

                                                                H+ H      H
   Light reactions                                           +   ++H H
                                                                 +H     H
                                                                         +
                                                            H H H + H+H+H +
                                                                         +
                                                                              +

                                                      ATP      H
 _______________________
        like in cellular respiration
    proteins in organelle membrane
    __________________

        ______________
      proton (H+)
       gradient across
       inner membrane
        find the double membrane!
      ATP synthase
       enzyme
AP Biology
ETC of Respiration
Mitochondria transfer chemical energy from food molecules
into chemical energy of ATP
     use electron carrier ___________




                                         generate H2O

 AP Biology
ETC of Photosynthesis      Chloroplasts transform light energy
                           into chemical energy of ATP
                                use electron carrier ___________




             generate O2

AP Biology
The ATP that “Jack” built
   photosynthesis             respiration
      sunlight                 breakdown of C6H12O6
                                                       H+
                                                            H+        H+         H+

                                                       H+              H+
                                                                 H+              H+
         moves the electrons
         runs the pump
         pumps the protons
         builds the gradient
         drives the flow of protons
          through ATP synthase              ADP + Pi
         bonds Pi to ADP                      ATP
         generates the ATP                                                 H+

AP Biology   … that evolution built
Pigments of photosynthesis




                                            How does this
                                         molecular structure
                                          fit its function?

 Chlorophylls & other pigments
      embedded in thylakoid membrane
      arranged in a “photosystem”
         collection of molecules
 AP 
    Biology
       structure-function relationship
A Look at Light
     The spectrum of color




             V   I   B   G   Y   O   R


AP Biology
Light: absorption spectra
       Photosynthesis gets energy by absorbing
         wavelengths of light
             _______________________
                 absorbs best in red & blue wavelengths & least in green
             accessory pigments with different structures
              absorb light of different wavelengths
                 chlorophyll b, carotenoids, xanthophylls

   Why are
plants green?




 AP Biology
Photosystems of photosynthesis
    2 photosystems in thylakoid membrane
         collections of chlorophyll molecules
         act as light-gathering molecules

         _________________
                                reaction
              __________________ center
              P680 = absorbs 680nm
              wavelength red light
            _________________
              __________________
              P700 = absorbs 700nm
              wavelength red light
                                             antenna
AP Biology                                   pigments
ETC of Photosynthesis
                  chlorophyll a
             ______________
                                  chlorophyll b
                         ______________




AP Biology
ETC of Photosynthesis




     sun

                1
                    e
                    e




             Photosystem II
                  P680
AP Biology    chlorophyll a
Inhale, baby!
                                              ETC of Photosynthesis
                                              chloroplast                             thylakoid
                                                                         +H H     +    +
                                                                  H H H + H+H+H +
                                                                   +     +        +

                                                                      H +H       H
                                                                         +H+ H
                                                                               +
                                                                  H+ H+H + H+H+H +
                                                                                  +

                                                            ATP       H +H       H




                                               Plants SPLIT water!
                                                       H H
                1                                       O
       2
                    e
                    e
                                               O                             +H
                                              O                    H+


                 e e                                                e-
                                                                         e-

             Photosystem II              fill the e– vacancy
                  P680
AP Biology    chlorophyll a
ETC of Photosynthesis

                                                        chloroplast                         thylakoid
                                                                                          H+ H+ +
                                                                                  H+ H+H + H+H+H +
                                                                                        +

                                                                                      H+ H      H
                                                                                         +H+ H
                                                                                               +
                                                                                  H+ H+H + H+H+H +
                                                                                                  +

                                                                           ATP        H+ H       H



                        e
                        e                                   3
                1
       2
                    e       H+
                    e

                                  4                                         ATP
                                                   H+
                                              H+
                                                   H+       H+        H+
                                              H+    H   +   H+        H+
                                                                            _________________
                                                                            _________________
             Photosystem II
                  P680             ADP + Pi

              chlorophyll a      ATP
AP Biology
                                                                 H+
ETC of Photosynthesis




                     e
                       e
                                          e                            cy
                                          e                      a   n
                                                                            sun
                                                          –   vac
                                                          e
                                      5               e
                                                   th


                              e
                                                 l
                                              fil


                              e
                                     e e

                                  Photosystem I
                                       P700
             Photosystem II
                                   chlorophyll b
                  P680
AP Biology    chlorophyll a
ETC of Photosynthesis

                                                             electron carrier




                                                     e
                                                      e
                                                             6
                                                 e
                                                 e

                                                5
                                                             sun




                                            Photosystem I
                                                 P700
             Photosystem II
                                             chlorophyll b
                  P680        $$ in the bank…
AP Biology    chlorophyll a   reducing power!
sun
                                      ETC of Photosynthesis




                                       e
                         e




                                         e
                         e


                                        H+
                                 H H H+ H+ H +
                                    +         +
                             O    +
                                       H+
                                      + H+ H+
                                              H
                                    H
             split H2O




                                                  ATP
AP Biology
ETC of Photosynthesis
      ETC uses light energy to produce
            ATP & NADPH
               go to Calvin cycle
      PS II absorbs light
            excited electron passes from chlorophyll to
             “primary electron acceptor”
            need to replace electron in chlorophyll
            enzyme extracts electrons from H2O & supplies
             them to chlorophyll
               splits H2O
               O combines with another O to form O2
               O2 released to atmosphere
AP Biology     and we breathe easier!
Experimental evidence
     Where did the O2 come from?
            radioactive tracer = O18
    Experiment 1
        6CO2 + 6H2O + light → C6H12O6 + 6O2
                     energy

    Experiment 2
        6CO2 + 6H2O + light → C6H12O6 + 6O2
                     energy


Proved O2 came from H2O not CO2 = plants split H2O!
AP Biology
Noncyclic Photophosphorylation
     Light reactions
        elevate electrons in
        2 steps (PS II & PS I)
            ____________________
             ____________________
            ____________________
             ____________________

                                    ATP




AP Biology
Cyclic photophosphorylation
  If PS I can’t pass electron
   to NADP…it cycles back
   to PS II & makes more
   ATP, but no NADPH
     coordinates light
      reactions to Calvin cycle
     Calvin cycle uses more

      ATP than NADPH
                                  ATP




   18 ATP +
  12 NADPH
              → 1 C6H12O6
AP Biology
Photophosphorylation
                    cyclic
             photophosphorylation




                                                  NADP




                                         NONcyclic
                                    photophosphorylation


                         ATP

AP Biology
Photosynthesis summary
     Where did the energy come from?
     Where did the electrons come from?
     Where did the H2O come from?
     Where did the O2 come from?
     Where did the O2 go?
     Where did the H+ come from?
     Where did the ATP come from?
     What will the ATP be used for?
     Where did the NADPH come from?
     What will the NADPH be used for?
AP Biology                  …stay tuned for the Calvin cycle
You can grow if you
               Ask Questions!




AP Biology                    2008-2009

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46 ch10photosynthesis2008print

  • 1. Photosynthesis: Life from Light and Air AP Biology 2008-2009
  • 2. Energy needs of life  All life needs a constant input of energy  __________________________  get their energy from “eating others” consumers  eat food = other organisms = organic molecules  make energy through respiration  __________________________  produce their own energy (from “self”)  convert energy of sunlight producers  build organic molecules (CHO) from CO2  make energy & synthesize sugars through AP Biology photosynthesis
  • 3. How are they connected? Heterotrophs making energy & organic molecules from ingesting organic molecules glucose + oxygen → carbon + water + energy dioxide C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP oxidation = exergonic Autotrophs Where’s making energy & organic molecules from light energy the ATP? carbon + water + energy → glucose + oxygen dioxide 6CO2 + 6H2O + light → C6H12O6 + 6O2 energy AP Biology reduction = endergonic
  • 4. What does it mean to be a plant  Need to…  collect light energy ATP  transform it into chemical energy  store light energy  in a stable form to be moved around glucose the plant or stored  need to get building block atoms CO from the environment 2 H 2O  C,H,O,N,P,K,S,Mg N  produce all organic molecules K P needed for growth …  carbohydrates, proteins, lipids, nucleic acids AP Biology
  • 5. Plant structure  Obtaining raw materials  __________  _______________________  __________  _______________________  __________  _______________________  __________  N, P, K, S, Mg, Fe…  _______________________ AP Biology
  • 6. stomate ______________ AP ______________ Biology
  • 7. Chloroplasts cross section absorb leaves of leaf sunlight & CO2 CO2 chloroplasts in plant cell chloroplasts chloroplast contain chlorophyll make AP Biology energy & sugar
  • 8. chloroplast H+ H +H + H++ + + Plant structure H H + + + H H H ATP H+ H thylakoid  Chloroplasts  _________________  _________________ outer membrane inner membrane  fluid-filled interior  _________________ stroma  _________________  Thylakoid membrane contains thylakoid granum  chlorophyll molecules  electron transport chain  ATP synthase  H+ gradient built up within thylakoid sac AP Biology
  • 9. Photosynthesis  ____________________  _________________________  _________________________  convert solar energy to chemical energy  ATP & NADPH It’s not the  ____________________ Dark Reactions!  _________________________  _________________________  uses chemical energy (ATP & NADPH) to reduce CO2 & synthesize C6H12O6 AP Biology
  • 10. chloroplast thylakoid H+ H+ + H+ H+H + H+H+H + + H+ H H Light reactions + ++H H +H H + H H H + H+H+H + + + ATP H  _______________________  like in cellular respiration  proteins in organelle membrane  __________________  ______________  proton (H+) gradient across inner membrane  find the double membrane!  ATP synthase enzyme AP Biology
  • 11. ETC of Respiration Mitochondria transfer chemical energy from food molecules into chemical energy of ATP  use electron carrier ___________ generate H2O AP Biology
  • 12. ETC of Photosynthesis Chloroplasts transform light energy into chemical energy of ATP  use electron carrier ___________ generate O2 AP Biology
  • 13. The ATP that “Jack” built photosynthesis respiration sunlight breakdown of C6H12O6 H+ H+ H+ H+ H+ H+ H+ H+  moves the electrons  runs the pump  pumps the protons  builds the gradient  drives the flow of protons through ATP synthase ADP + Pi  bonds Pi to ADP ATP  generates the ATP H+ AP Biology … that evolution built
  • 14. Pigments of photosynthesis How does this molecular structure fit its function?  Chlorophylls & other pigments  embedded in thylakoid membrane  arranged in a “photosystem”  collection of molecules AP  Biology structure-function relationship
  • 15. A Look at Light  The spectrum of color V I B G Y O R AP Biology
  • 16. Light: absorption spectra  Photosynthesis gets energy by absorbing wavelengths of light  _______________________  absorbs best in red & blue wavelengths & least in green  accessory pigments with different structures absorb light of different wavelengths  chlorophyll b, carotenoids, xanthophylls Why are plants green? AP Biology
  • 17. Photosystems of photosynthesis  2 photosystems in thylakoid membrane  collections of chlorophyll molecules  act as light-gathering molecules  _________________ reaction  __________________ center  P680 = absorbs 680nm wavelength red light  _________________  __________________  P700 = absorbs 700nm wavelength red light antenna AP Biology pigments
  • 18. ETC of Photosynthesis chlorophyll a ______________ chlorophyll b ______________ AP Biology
  • 19. ETC of Photosynthesis sun 1 e e Photosystem II P680 AP Biology chlorophyll a
  • 20. Inhale, baby! ETC of Photosynthesis chloroplast thylakoid +H H + + H H H + H+H+H + + + + H +H H +H+ H + H+ H+H + H+H+H + + ATP H +H H Plants SPLIT water! H H 1 O 2 e e O +H O H+ e e e- e- Photosystem II fill the e– vacancy P680 AP Biology chlorophyll a
  • 21. ETC of Photosynthesis chloroplast thylakoid H+ H+ + H+ H+H + H+H+H + + H+ H H +H+ H + H+ H+H + H+H+H + + ATP H+ H H e e 3 1 2 e H+ e 4 ATP H+ H+ H+ H+ H+ H+ H + H+ H+ _________________ _________________ Photosystem II P680 ADP + Pi chlorophyll a ATP AP Biology H+
  • 22. ETC of Photosynthesis e e e cy e a n sun – vac e 5 e th e l fil e e e Photosystem I P700 Photosystem II chlorophyll b P680 AP Biology chlorophyll a
  • 23. ETC of Photosynthesis electron carrier e e 6 e e 5 sun Photosystem I P700 Photosystem II chlorophyll b P680 $$ in the bank… AP Biology chlorophyll a reducing power!
  • 24. sun ETC of Photosynthesis e e e e H+ H H H+ H+ H + + + O + H+ + H+ H+ H H split H2O ATP AP Biology
  • 25. ETC of Photosynthesis  ETC uses light energy to produce  ATP & NADPH  go to Calvin cycle  PS II absorbs light  excited electron passes from chlorophyll to “primary electron acceptor”  need to replace electron in chlorophyll  enzyme extracts electrons from H2O & supplies them to chlorophyll  splits H2O  O combines with another O to form O2  O2 released to atmosphere AP Biology  and we breathe easier!
  • 26. Experimental evidence  Where did the O2 come from?  radioactive tracer = O18 Experiment 1 6CO2 + 6H2O + light → C6H12O6 + 6O2 energy Experiment 2 6CO2 + 6H2O + light → C6H12O6 + 6O2 energy Proved O2 came from H2O not CO2 = plants split H2O! AP Biology
  • 27. Noncyclic Photophosphorylation  Light reactions elevate electrons in 2 steps (PS II & PS I)  ____________________ ____________________  ____________________ ____________________ ATP AP Biology
  • 28. Cyclic photophosphorylation  If PS I can’t pass electron to NADP…it cycles back to PS II & makes more ATP, but no NADPH  coordinates light reactions to Calvin cycle  Calvin cycle uses more ATP than NADPH ATP 18 ATP + 12 NADPH → 1 C6H12O6 AP Biology
  • 29. Photophosphorylation cyclic photophosphorylation NADP NONcyclic photophosphorylation ATP AP Biology
  • 30. Photosynthesis summary Where did the energy come from? Where did the electrons come from? Where did the H2O come from? Where did the O2 come from? Where did the O2 go? Where did the H+ come from? Where did the ATP come from? What will the ATP be used for? Where did the NADPH come from? What will the NADPH be used for? AP Biology …stay tuned for the Calvin cycle
  • 31. You can grow if you Ask Questions! AP Biology 2008-2009

Notas del editor

  1. So, in effect, photosynthesis is respiration run backwards powered by light. Cellular Respiration oxidize C 6 H 12 O 6  CO 2 & produce H 2 O fall of electrons downhill to O 2 exergonic Photosynthesis reduce CO 2  C 6 H 12 O 6 & produce O 2 boost electrons uphill by splitting H 2 O endergonic
  2. A typical mesophyll cell has 30-40 chloroplasts, each about 2-4 microns by 4-7 microns long. Each chloroplast has two membranes around a central aqueous space, the stroma. In the stroma are membranous sacs, the thylakoids. These have an internal aqueous space, the thylakoid lumen or thylakoid space. Thylakoids may be stacked into columns called grana.
  3. Not accidental that these 2 systems are similar, because both derived from the same primitive ancestor.
  4. NADH is an input ATP is an output O 2 combines with H + ’s to form water Electron is being handed off from one electron carrier to another -- proteins, cytochrome proteins & quinone lipids So what if it runs in reverse??
  5. Two places where light comes in. Remember photosynthesis is endergonic -- the electron transport chain is driven by light energy. Need to look at that in more detail on next slide
  6. Photons are absorbed by clusters of pigment molecules ( antenna molecules) in the thylakoid membrane. When any antenna molecule absorbs a photon, it is transmitted from molecule to molecule until it reaches a particular chlorophyll a molecule = the reaction center . At the reaction center is a primary electron acceptor which removes an excited electron from the reaction center chlorophyll a. This starts the light reactions. Don’t compete with each other, work synergistically using different wavelengths.
  7. Two places where light comes in. Remember photosynthesis is endergonic -- the electron transport chain is driven by light energy. Need to look at that in more detail on next slide
  8. PS II absorbs light Excited electron passes from chlorophyll to the primary electron acceptor Need to replace electron in chlorophyll An enzyme extracts electrons from H 2 O & supplies them to the chlorophyll This reaction splits H 2 O into 2 H + & O - which combines with another O - to form O 2 O 2 released to atmosphere Chlorophyll absorbs light energy (photon) and this moves an electron to a higher energy state Electron is handed off down chain from electron acceptor to electron acceptor In process has collected H + ions from H 2 O & also pumped by Plastoquinone within thylakoid sac. Flow back through ATP synthase to generate ATP.
  9. Need a 2nd photon -- shot of light energy to excite electron back up to high energy state. 2nd ETC drives reduction of NADP to NADPH. Light comes in at 2 points. Produce ATP & NADPH
  10. Need a 2nd photon -- shot of light energy to excite electron back up to high energy state. 2nd ETC drives reduction of NADP to NADPH. Light comes in at 2 points. Produce ATP & NADPH
  11. Two places where light comes in. Remember photosynthesis is endergonic -- the electron transport chain is driven by light energy. Need to look at that in more detail on next slide
  12. 1 photosystem is not enough. Have to lift electron in 2 stages to a higher energy level. Does work as it falls. First, produce ATP -- but producing ATP is not enough. Second, need to produce organic molecules for other uses & also need to produce a stable storage molecule for a rainy day (sugars). This is done in Calvin Cycle!
  13. Where did the energy come from? The Sun Where did the electrons come from? Chlorophyll Where did the H 2 O come from? The ground through the roots/xylem Where did the O 2 come from? The splitting of water Where did the O 2 go? Out stomates to air Where did the H + come from? The slitting of water Where did the ATP come from? Photosystem 2: Chemiosmosis (H+ gradient) What will the ATP be used for? The work of plant life! Building sugars Where did the NADPH come from? Reduction of NADP (Photosystem 1) What will the NADPH be used for? Calvin cycle / Carbon fixation