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AP Biology

2007-2008
Photosynthesis:
Life from Light and Air

AP Biology

2007-2008
Energy needs of life
 All life needs a constant input of energy


Heterotrophs (Animals)

 get their energy from “eatin...
How are they connected?
Heterotrophs
making energy & organic molecules from ingesting organic molecules

glucose + oxygen ...
What does it mean to be a plant
 Need to…


collect light energy

ATP

 transform it into chemical energy


glucose

...
Plant structure
 Obtaining raw materials


sunlight
 leaves = solar collectors



CO2
 stomates = gas exchange



H2...
stomate

transpiration
AP gas exchange
Biology
Chloroplasts
leaves

cross section
of leaf

absorb
sunlight & CO2
CO2

chloroplasts
in plant cell

chloroplast
AP Biology
...
chloroplast

Plant structure

+
+
H+ H +H + H++
H H
+ H H H
H+ H
thylakoid
+

ATP

+

 Chloroplasts



double membrane
...
Photosynthesis
 Light reactions
light-dependent reactions
 energy conversion reactions


 convert solar energy to chem...
chloroplast

Light reactions
 Electron Transport Chain
 like in cellular respiration

proteins in organelle membrane
 e...
ETC of Respiration
Mitochondria transfer chemical energy from food molecules
into chemical energy of ATP


use electron c...
ETC of Photosynthesis

Chloroplasts transform light energy
into chemical energy of ATP


generates O2
AP Biology

use ele...
The ATP that “Jack” built
photosynthesis

sunlight

respiration

breakdown of C6H12O6
H+
H+
H+

 moves the electrons
 ru...
Pigments of photosynthesis

How does this
molecular structure
fit its function?

 Chlorophylls & other pigments



embe...
A Look at Light
 The spectrum of color

V

AP Biology

I

B

G

Y

O

R
Light: absorption spectra
 Photosynthesis gets energy by absorbing
wavelengths of light


chlorophyll a
 absorbs best i...
Photosystems of photosynthesis
 2 photosystems in thylakoid membrane
collections of chlorophyll molecules
 act as light-...
chlorophyll a

ETC of Photosynthesis

Photosystem II
chlorophyll b

Photosystem I

AP Biology
ETC of Photosynthesis

sun
1

e
e

AP Biology

Photosystem II
P680
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 +
H
...
ETC of Photosynthesis
chloroplast

thylakoid

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

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

e

e

...
e

e

ETC of Photosynthesis

e
e
–

e

e

5

e
th
l
fil

e e

AP Biology

Photosystem II
P680
chlorophyll a

Photosystem I...
ETC of Photosynthesis

e

e

electron carrier

6

e
e
5

AP Biology

Photosystem II
P680
chlorophyll a

Photosystem I
P700...
ETC of Photosynthesis

sun

e

e

e

e

sun

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

O
split H2O

+

to Calvin Cycle

ATP
AP...
ETC of Photosynthesis
 ETC uses light energy to produce


ATP & NADPH
 go to Calvin cycle

 PS II absorbs light



...
Experimental evidence
 Where did the O2 come from?


radioactive tracer = O18

Experiment 1
6CO2 + 6H2O + light → C6H12O...
Noncyclic Photophosphorylation
 Light reactions elevate
electrons in
2 steps (PS II & PS I)


PS II generates
energy as ...
Cyclic photophosphorylation
 If PS I can’t pass electron
to NADP…it cycles back
to PS II & makes more
ATP, but no NADPH

...
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?
Whe...
You can grow if you
Ask Questions!

AP Biology

2007-2008
Ghosts of Lectures Past
(storage)

AP Biology

2007-2008
Stomates

AP Biology
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46 ch10photosynthesis2008

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46 ch10photosynthesis2008

  1. 1. AP Biology 2007-2008
  2. 2. Photosynthesis: Life from Light and Air AP Biology 2007-2008
  3. 3. Energy needs of life  All life needs a constant input of energy  Heterotrophs (Animals)  get their energy from “eating others” consumers  eat food = other organisms = organic molecules  make energy through respiration  Autotrophs (Plants)  produce their own energy (from “self”) producers  convert energy of sunlight  build organic molecules (CHO) from CO2  make energy & synthesize sugars through AP Biology photosynthesis
  4. 4. 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 making energy & organic molecules from light energy Where’s the ATP? carbon + water + energy → glucose + oxygen dioxide 6CO2 + 6H2O + light → C6H12O6 + 6O2 energy AP Biology reduction = endergonic
  5. 5. What does it mean to be a plant  Need to…  collect light energy ATP  transform it into chemical energy  glucose  store light energy  in a stable form to be moved around the plant or stored need to get building block atoms CO 2 from the environment H 2O  C,H,O,N,P,K,S,Mg  produce all organic molecules needed for growth N K P …  carbohydrates, proteins, lipids, nucleic acids AP Biology
  6. 6. Plant structure  Obtaining raw materials  sunlight  leaves = solar collectors  CO2  stomates = gas exchange  H2O  uptake from roots  nutrients  N, P, K, S, Mg, Fe…  uptake from roots AP Biology
  7. 7. stomate transpiration AP gas exchange Biology
  8. 8. Chloroplasts leaves cross section of leaf absorb sunlight & CO2 CO2 chloroplasts in plant cell chloroplast AP Biology chloroplasts contain chlorophyll make energy & sugar
  9. 9. chloroplast Plant structure + + H+ H +H + H++ H H + H H H H+ H thylakoid + ATP +  Chloroplasts   double membrane stroma outer membrane inner membrane  fluid-filled interior   thylakoid sacs grana stacks stroma  Thylakoid membrane contains    chlorophyll molecules electron transport chain ATP synthase  H+ gradient built up within thylakoid sac AP Biology thylakoid granum
  10. 10. Photosynthesis  Light reactions light-dependent reactions  energy conversion reactions   convert solar energy to chemical energy  ATP & NADPH  Calvin cycle It’s not the Dark Reactions! light-independent reactions  sugar building reactions   uses chemical energy (ATP & NADPH) to reduce CO2 & synthesize C6H12O6 AP Biology
  11. 11. chloroplast Light reactions  Electron Transport Chain  like in cellular respiration proteins in organelle membrane  electron acceptors   NADPH  proton (H+) gradient across inner membrane  find the double membrane!  ATP synthase enzyme AP Biology thylakoid H+ H+ + H+ H+H + H+H+H + H H+ H + ATP +H H + H H H + H+H+H + H +H H + + + +
  12. 12. ETC of Respiration Mitochondria transfer chemical energy from food molecules into chemical energy of ATP  use electron carrier NADH generates H2O AP Biology
  13. 13. ETC of Photosynthesis Chloroplasts transform light energy into chemical energy of ATP  generates O2 AP Biology use electron carrier NADPH
  14. 14. The ATP that “Jack” built photosynthesis sunlight respiration breakdown of C6H12O6 H+ H+ H+  moves the electrons  runs the pump H+ H+ H+ H+ H+  pumps the protons  builds the gradient  drives the flow of protons through ATP synthase  bonds Pi to ADP  generates the ATP AP Biology … that evolution built ADP + Pi ATP H+
  15. 15. 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
  16. 16. A Look at Light  The spectrum of color V AP Biology I B G Y O R
  17. 17. Light: absorption spectra  Photosynthesis gets energy by absorbing wavelengths of light  chlorophyll a  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
  18. 18. Photosystems of photosynthesis  2 photosystems in thylakoid membrane collections of chlorophyll molecules  act as light-gathering molecules  Photosystem II reaction   chlorophyll a  P680 = absorbs 680nm center wavelength red light  Photosystem I  chlorophyll b  P700 = absorbs 700nm wavelength red light AP Biology antenna pigments
  19. 19. chlorophyll a ETC of Photosynthesis Photosystem II chlorophyll b Photosystem I AP Biology
  20. 20. ETC of Photosynthesis sun 1 e e AP Biology Photosystem II P680 chlorophyll a
  21. 21. 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 + H +H H + ATP + + Plants SPLIT water! H H 1 e- e e fill the e– vacancy AP Biology Photosystem II P680 chlorophyll a e- H+ +H O O H H e e O 2
  22. 22. ETC of Photosynthesis chloroplast thylakoid H+ H+ + H+ H+H + H+H+H + H H+ H + + +H+ H + H+ H+H + H+H+H + H H+ H e e ATP 3 2 1 e e H+ 4 ATP H+ H+ H+ AP Biology Photosystem II P680 chlorophyll a H+ to Calvin Cycle H+ H+ + H+ H H+ ADP + Pi ATP H+ energy to build carbohydrates
  23. 23. e e ETC of Photosynthesis e e – e e 5 e th l fil e e AP Biology Photosystem II P680 chlorophyll a Photosystem I P700 chlorophyll b e cy n ca va sun
  24. 24. ETC of Photosynthesis e e electron carrier 6 e e 5 AP Biology Photosystem II P680 chlorophyll a Photosystem I P700 chlorophyll b $$ in the bank… reducing power! N Cal ADPH vin Cyc to sun le
  25. 25. ETC of Photosynthesis sun e e e e sun + H + H H H+ H+ H + H H+ + H+ H+ H + O split H2O + to Calvin Cycle ATP AP Biology
  26. 26. ETC of Photosynthesis  ETC uses light energy to produce  ATP & NADPH  go to Calvin cycle  PS II absorbs light    AP Biology 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  and we breathe easier!
  27. 27. 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
  28. 28. Noncyclic Photophosphorylation  Light reactions elevate electrons in 2 steps (PS II & PS I)  PS II generates energy as ATP  PS I generates reducing power as NADPH ATP AP Biology
  29. 29. 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 AP Biology → 1 C6H12O6
  30. 30. Photophosphorylation cyclic photophosphorylation NADP NONcyclic photophosphorylation ATP AP Biology
  31. 31. 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
  32. 32. You can grow if you Ask Questions! AP Biology 2007-2008
  33. 33. Ghosts of Lectures Past (storage) AP Biology 2007-2008
  34. 34. Stomates AP Biology

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