Photosynthesis Reactions
Electron carriers <ul><li>Electrons in chlorophyll </li></ul><ul><li>Sun excites them </li></ul><ul><li>Electrons gain E <...
 
Photosystems <ul><li>Clusters of chlorophyll and other pigments in the thylakoid membrane (organized by a set of proteins ...
 
 
Light Dependent Reactions <ul><li>Produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH </li...
<ul><li>High-E electrons move through the ETC from photosystem II to photosystem I </li></ul><ul><li>Energy from electrons...
<ul><li>Pigments in photosystem I use Energy from light to re-energize the electrons </li></ul><ul><li>NADP+ then picks up...
<ul><li>As electrons are passed from chlorophyll to NADP+, H+ ions are pumped across membrane </li></ul><ul><li>Inside of ...
ETC proteins <ul><li>Photosystem II (recieves light & splits water) </li></ul><ul><ul><li>Oxygen-evolving complex </li></u...
 
 
 
 
 
Overview of Light Dependent Rxn <ul><li>Use: </li></ul><ul><ul><li>ADP </li></ul></ul><ul><ul><li>NADP+ </li></ul></ul><ul...
Calvin Cycle/ Light-Independent Reactions <ul><li>So what do we have from pour light-dependent rxns? </li></ul><ul><ul><li...
 
Step 1 <ul><li>Six carbon dioxide molecules enter cycle from atmosphere </li></ul><ul><ul><li>Enzyme adds each CO2 molecul...
 
Step 2 <ul><li>Twelve 3-carbon molecules are converted into higher energy forms using energy from ATP and high-E electrons...
 
Step 3 <ul><li>Two of the G3Ps (twelve 3-carbon molecules) are removed from the cycle </li></ul><ul><li>Plant uses these t...
 
Step 4 <ul><li>Remaining ten G3Ps (3-carbon molecules) use ATP and rearrange themselves </li></ul><ul><ul><li>ADP and NADP...
 
Calvin cycle overview <ul><li>Uses: </li></ul><ul><ul><li>Six molecules of CO2 </li></ul></ul><ul><ul><li>NADPH </li></ul>...
 
 
 
Photosynthesis overview <ul><li>Two sets of reactions work together </li></ul><ul><ul><li>Light dependent </li></ul></ul><...
Factors that effect rate of photosyntehsis <ul><li>Water availability </li></ul><ul><ul><li>Shortage of water can slow or ...
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Photosynthesis 2

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Photosynthesis 2

  1. 1. Photosynthesis Reactions
  2. 2. Electron carriers <ul><li>Electrons in chlorophyll </li></ul><ul><li>Sun excites them </li></ul><ul><li>Electrons gain E </li></ul><ul><li>These high E electrons require special carrier </li></ul><ul><li>High E e- are similar to hot coals that need to be transferred </li></ul><ul><li>Electron carriers needed to transport high-E e- </li></ul><ul><li>NADP+ </li></ul><ul><ul><li>Nicotinamide adenine dinucleotide phosphate </li></ul></ul><ul><ul><li>Accepts 2 high-E e- to become NADPH </li></ul></ul><ul><ul><li>This is how energy (e-) from sun can be trapped in chemical form </li></ul></ul><ul><ul><li>NADPH carries high-E e- from chlorophyll to other parts of the chloroplast </li></ul></ul><ul><ul><li>Help build molecules, such as glucose </li></ul></ul>
  3. 4. Photosystems <ul><li>Clusters of chlorophyll and other pigments in the thylakoid membrane (organized by a set of proteins in the plant cell) </li></ul><ul><li>Contain few hundred pigment molecules </li></ul><ul><ul><li>Chlorophyll a </li></ul></ul><ul><ul><li>Chlorophyll b </li></ul></ul><ul><ul><li>Carotene/carotenoids </li></ul></ul><ul><li>Light-collecting unit of the cell </li></ul><ul><li>Solar panel </li></ul><ul><li>Photosystem II and Photosystem II </li></ul>
  4. 7. Light Dependent Reactions <ul><li>Produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH </li></ul><ul><li>Take place in the THYLAKOID membrane of chloroplast </li></ul><ul><li>Begins with photosystem II </li></ul><ul><ul><li>(this was discovered after photosystem I but actually occurs before it) </li></ul></ul><ul><ul><li>Photosystem II traps light E and transfers excited e- to an ETC </li></ul></ul><ul><ul><li>“ water-splitting” photosystem </li></ul></ul><ul><ul><ul><li>Light absorbed by photosystem II is used to break-up water molecules into high-E electrons, oxygen, and H+ ions </li></ul></ul></ul><ul><ul><ul><li>2 electrons  replace lost e- in chlorophyll </li></ul></ul></ul><ul><ul><ul><li>2 H+ ions  released into the inside of the thylakoid membrane </li></ul></ul></ul><ul><ul><ul><li>1 oxygen atom  oxygen released into atmosphere </li></ul></ul></ul><ul><li>Electrons in chlorophyll are excited  passed along ETC  do electrons in chlorophyll run out? </li></ul><ul><ul><li>No: the high-E electrons lost by the chlorophyll are replaced by the electrons from “water splitting” </li></ul></ul>
  5. 8. <ul><li>High-E electrons move through the ETC from photosystem II to photosystem I </li></ul><ul><li>Energy from electrons is used by molecules in the ETC to transport H+ ions from the stroma into the inner thylakoid space </li></ul>
  6. 9. <ul><li>Pigments in photosystem I use Energy from light to re-energize the electrons </li></ul><ul><li>NADP+ then picks up these high-E electrons and H+ ions at the outer surface of the thylakoid membrane </li></ul><ul><li>NADP+ becomes NADPH </li></ul>
  7. 10. <ul><li>As electrons are passed from chlorophyll to NADP+, H+ ions are pumped across membrane </li></ul><ul><li>Inside of thylakoid membrane fills up with positive H+ ions, outside in negative </li></ul><ul><li>Chemosmosis occurs </li></ul><ul><li>ATP synthase turns making ADP  ATP </li></ul>
  8. 11. ETC proteins <ul><li>Photosystem II (recieves light & splits water) </li></ul><ul><ul><li>Oxygen-evolving complex </li></ul></ul><ul><ul><li>Plastoquinone </li></ul></ul><ul><ul><li>Cytochrome </li></ul></ul><ul><ul><li>Plastocyanin </li></ul></ul><ul><li>Photosystem I (receives more light) </li></ul><ul><ul><li>Ferredoxin </li></ul></ul><ul><ul><li>Ferrdoxin-NADP reductase </li></ul></ul><ul><ul><ul><li>NADP  NADPH </li></ul></ul></ul><ul><ul><li>ATP synthase </li></ul></ul><ul><ul><ul><li>ADP  ATP </li></ul></ul></ul>
  9. 17. Overview of Light Dependent Rxn <ul><li>Use: </li></ul><ul><ul><li>ADP </li></ul></ul><ul><ul><li>NADP+ </li></ul></ul><ul><ul><li>Water </li></ul></ul><ul><li>Produce: </li></ul><ul><ul><li>Oxygen </li></ul></ul><ul><ul><li>ATP </li></ul></ul><ul><ul><li>NADPH </li></ul></ul><ul><li>Why are these products important? </li></ul><ul><ul><li>Provide energy to build energy-containing sugars from low-energy compounds in Calvin cycle </li></ul></ul>
  10. 18. Calvin Cycle/ Light-Independent Reactions <ul><li>So what do we have from pour light-dependent rxns? </li></ul><ul><ul><li>High-E electrons stored in ATP and NADPH </li></ul></ul><ul><ul><li>“ chemical energy” </li></ul></ul><ul><ul><li>But plants cannot store this chemical energy for more than a few minutes…must change this chemical energy into something that can be stored for long periods of time </li></ul></ul><ul><li>Calvin cycle </li></ul><ul><ul><li>Uses ATP and NADPH from light-dependent rxn to produce high-E sugars </li></ul></ul>
  11. 20. Step 1 <ul><li>Six carbon dioxide molecules enter cycle from atmosphere </li></ul><ul><ul><li>Enzyme adds each CO2 molecule to a Ribose biphosphate, RuBP molecule (a 5-carbon molecule) making six unstable 6-carbon molecules </li></ul></ul><ul><li>The six unstable 6-carbon molecules immediately break off into 12 3-carbon molecules called 3-phosphoglycerate, 3-PGA </li></ul>
  12. 22. Step 2 <ul><li>Twelve 3-carbon molecules are converted into higher energy forms using energy from ATP and high-E electrons from NADPH </li></ul><ul><ul><li>Twelve 3-PGAs are converted into twelve energized Glyceraldehyde 3-phosphates (G3P). </li></ul></ul><ul><ul><ul><li>3-PGAs + ATP  1, 3-biphosphoglycerate </li></ul></ul></ul><ul><ul><ul><li>1, 3-biphosphoglycerate + NADPH  Glyceraldehyde 3-phosphate </li></ul></ul></ul>
  13. 24. Step 3 <ul><li>Two of the G3Ps (twelve 3-carbon molecules) are removed from the cycle </li></ul><ul><li>Plant uses these two G3Ps (3-carbon molecules) to make sugars, lipids, amino acids, and other compounds plant needs for metabolism and growth </li></ul>
  14. 26. Step 4 <ul><li>Remaining ten G3Ps (3-carbon molecules) use ATP and rearrange themselves </li></ul><ul><ul><li>ADP and NADP+ go back to light rxns </li></ul></ul><ul><li>Converted back into RuBP molecules (six 5-carbon molecules) </li></ul><ul><li>Calvin cycle begins again with six new CO2 molecules </li></ul>
  15. 28. Calvin cycle overview <ul><li>Uses: </li></ul><ul><ul><li>Six molecules of CO2 </li></ul></ul><ul><ul><li>NADPH </li></ul></ul><ul><ul><li>ATP </li></ul></ul><ul><li>Produces: </li></ul><ul><ul><li>One 6-carbon sugar “glucose” </li></ul></ul>
  16. 32. Photosynthesis overview <ul><li>Two sets of reactions work together </li></ul><ul><ul><li>Light dependent </li></ul></ul><ul><ul><ul><li>Trap energy of sunlight into chemical form </li></ul></ul></ul><ul><ul><li>Calvin cycle/light independent </li></ul></ul><ul><ul><ul><li>Use chemical energy to produce stable-high energy sugars from carbon dioxide and water </li></ul></ul></ul>
  17. 33. Factors that effect rate of photosyntehsis <ul><li>Water availability </li></ul><ul><ul><li>Shortage of water can slow or stop photosyn. </li></ul></ul><ul><ul><li>Adaptations </li></ul></ul><ul><ul><ul><li>Desert plants and conifers </li></ul></ul></ul><ul><ul><ul><ul><li>Waxy coating </li></ul></ul></ul></ul><ul><li>Temperature </li></ul><ul><ul><li>Photosyn. Depends on enzymes that function between 0*C and 35*C </li></ul></ul><ul><ul><li>Low temp. may cause photosyn. to stop </li></ul></ul><ul><li>Intensity of light </li></ul><ul><ul><li>Increase light intensity=increase rate of photosynthesis </li></ul></ul><ul><ul><li>After a certain level of intensity, plant reaches its max rate of photosynthesis </li></ul></ul>

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