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I. Photosynthesis

I. Photosynthesis. A. 2 Part Process – Light-Dependent Rxns – convert light energy into chemical energy (ATP) - Also called Light Rxns Light-Independent Rxns – uses ATP from light-dependent rxns to produce sugars Also called the Calvin Cycle and Dark Rxns.

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I. Photosynthesis

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  1. I. Photosynthesis A. 2 Part Process – • Light-Dependent Rxns – convert light energy into chemical energy (ATP) - Also called Light Rxns • Light-Independent Rxns – uses ATP from light-dependent rxns to produce sugars • Also called the Calvin Cycle and Dark Rxns 6CO2 + 6H2O→C6H12O6 + 6O2

  2. Summary of Rxns in Chloroplast 6CO2 + 6H2O→C6H12O6 + 6O2

  3. 6CO2 + 6H2O→C6H12O6 + 6O2

  4. B. Takes place in chloroplasts… Structure: 1. Thylakoids – saclike membranes • Contain photosystems (light-collecting units) that are made up of chlorophyll, other pigments and proteins • Chlorophyll absorbs most visible light except green, which is reflected 2. Grana – stacks of thylakoids 3. Stroma – space/area around thylakoids 6CO2 + 6H2O→C6H12O6 + 6O2

  5. 6CO2 + 6H2O→C6H12O6 + 6O2

  6. III. Electron carriers: NADP+ and NADPH A. NADP+ (Nicotinamide adenine dinucleotide phosphate) • Electron carrier –transfers electrons 2. Holds 2 electrons and H+ (hydrogen ion) 3. Combines with H+ to make NADPH • This conversion traps energy that is used in the dark rxns NO!

  7. IV. Light-Dependent Rxns A. Require light for energy B. Uses this energy with H2O (water) to produce: • ATP and NADPH and • oxygen (O2) C. Takes place in thylakoids D. Summary of steps:

  8. 1. Photosystem II absorbs light from the sun. • the energy splits water molecules into oxygen, H+ ions, and electrons • Chlorophylls’ electrons get excited by the light • Oxygen leaves the plant into atmosphere

  9. 2. excited electrons move down the electron transport chaintoPhotosystem Iand produce NADPH • Electrons combine with NADP+ and H+ found in the cell • this forms NADPH

  10. 3. H+ protons move outside the thylakoid and cause ADPand P to become ATP. • There is a higher concentration of H+ protons in the thylakoid membrane than in the stroma, so the H+ will move out into the stroma • As the H+ protons pass through ATP synthase (protein in thylakoid membrane) into the stroma the protein grabs ADP and a P and converts it into ATP

  11. Animations http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter10/animations.html# http://faculty.nl.edu/jste/noncyclic_photophosphorylation.htm http://www.johnkyrk.com/photosynthesis.html

  12. Simulating Light Rxns

  13. Thursday November 4th 1. What occurs at photosystem I? 2. What occurs at photosystem II?

  14. V. Light-Independent Rxns(Calvin Cycle or Dark Rxns) A. No light required B. Uses energy from ATP and NADPH to produce high-energy sugars • Sugars can store energy longer than energy molecules C. Takes place in stroma D. Summary of steps:

  15. 1. CO2 diffuses into the cell and combines with RuBP to form PGA. • molecules of RuBP (5-carbon sugar) are present in the cell • 1 carbon (from CO2) attaches to each RuBP • This 6-carbon is unstable and immediately splits in half • This leaves 3-carbon structures called PGA Ribulose BiPhosphate Phosphoglycerate

  16. 2. PGA is changed into PGAL • PGA interacts with ATP and NADPH (from light rxns) resulting in PGAL (new 3-carbon structure) • The ATP and NADPH are returned to the light rxns as ADP, NADP+ • 1 PGAL leaves the cycle to become glucose Phosphoglyceraldehyde

  17. 3. The PGAL is converted back into RuBP • The remaining PGAL rearrange into RuBP with ATP’s energy • Then it starts all over again 

  18. Summary • The Calvin Cycle continually occurs producing sugars (glucose) and taking CO2 out of the atmosphere. • Plants use sugars for energy and to build starches and cellulose for growth and development • Consumers eat plants and use the energy from the sugars

  19. Simulating Calvin Cycle

  20. Light- dependent reactions Calvin cycle Energy from sunlight Thylakoid membranes ATP Stroma NADPH High-energy sugars ATP NADPH O2 Chloroplasts Simplified Concept Map Concept Map Section 8-3 Photosynthesis includes takes place in uses use take place in to produce to produce of 6CO2 + 6H2O→C6H12O6 + 6O2 Go to Section:

  21. Light- dependent reactions Calvin cycle Energy from sunlight Thylakoid membranes ATP Stroma NADPH High-energy sugars ATP NADPH O2 Chloroplasts Simplified Concept Map Concept Map Section 8-3 Photosynthesis includes takes place in uses use take place in to produce to produce of 6CO2 + 6H2O→C6H12O6 + 6O2 Go to Section:

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