Recommandé
Contenu connexe
Tendances
Tendances (20)
En vedette
En vedette (20)
Similaire à Photosynthesis: How Plants Harvest Light Energy
Similaire à Photosynthesis: How Plants Harvest Light Energy (20)
Plus de Uconn Stamford
Plus de Uconn Stamford (20)
Dernier
Dernier (20)
Photosynthesis: How Plants Harvest Light Energy
- 1. © 2010 Pearson Education, Inc. THE BASICS OF PHOTOSYNTHESIS • Photosynthesis: – Is used by plants, some protists, and some bacteria – Transforms light energy into chemical energy – Uses carbon dioxide and water as starting materials • The chemical energy produced via photosynthesis is stored in the bonds of sugar molecules.
- 2. © 2010 Pearson Education, Inc. Chloroplasts: Sites of Photosynthesis • Chloroplasts are: – The site of photosynthesis – Found mostly in the interior cells of leaves
- 3. © 2010 Pearson Education, Inc. • Inside chloroplasts are membranous sacs called thylakoids, which are suspended in a thick fluid, called stroma. • Thylakoids are concentrated in stacks called grana. • The green color of chloroplasts is from chlorophyll, a light- absorbing pigment.
- 4. © 2010 Pearson Education, Inc. • Stomata are tiny pores in leaves where carbon dioxide enters and oxygen exits.
- 5. Leaf cross section Stomata Vein CO2 O2 Figure 7.2-1
- 6. Leaf cross section Stomata Vein CO2 O2 Interior cell LM StromaGranum Thylakoid Chloroplast Outer membrane Inner membrane TEM Figure 7.2-2
- 7. Leaf cross section Stomata Vein CO2 O2 Figure 7.2a
- 9. © 2010 Pearson Education, Inc. The Overall Equation for Photosynthesis • In the overall equation for photosynthesis, notice that: – The reactants of photosynthesis are the waste products of cellular respiration.
- 10. Carbon dioxide 6 O26 CO2 6 H2O C6H12O6 Water Glucose Photo- synthesis Oxygen gas Light energy Figure 7.UN1
- 11. © 2010 Pearson Education, Inc. • In photosynthesis: – Sunlight provides the energy – Electrons are boosted “uphill” and added to carbon dioxide – Sugar is produced
- 12. © 2010 Pearson Education, Inc. • During photosynthesis, water is split into: – Hydrogen – Oxygen • Hydrogen is transferred along with electrons and added to carbon dioxide to produce sugar. • Oxygen escapes through stomata into the atmosphere.
- 13. © 2010 Pearson Education, Inc. A Photosynthesis Road Map • Photosynthesis occurs in two stages: – The light reactions convert solar energy to chemical energy – The Calvin cycle uses the products of the light reactions to make sugar from carbon dioxide Blast Animation: Photosynthesis: Light-Independent Reaction
- 16. © 2010 Pearson Education, Inc. How Photosystems Harvest Light Energy • Light behaves as photons, discrete packets of energy.
- 17. © 2010 Pearson Education, Inc. • Chlorophyll molecules absorb photons. – Electrons in the pigment gain energy. – As the electrons fall back to their ground state, energy is released as heat or light.
- 18. Light Photon Heat Light (fluorescence) Ground state Chlorophyll molecule Excited state e– (a) Absorption of a photon Figure 7.8a
- 19. © 2010 Pearson Education, Inc. • A photosystem is a group of chlorophyll and other molecules that function as a light-gathering antenna.
- 22. Chloroplast Thylakoid membrane Pigment molecules Antenna pigment molecules Primary electron acceptor Reaction- center chlorophyll a Photon Electron transfer Reaction center Photosystem Transfer of energy Figure 7.9-3
- 23. © 2010 Pearson Education, Inc. How the Light Reactions Generate ATP and NADPH • Two types of photosystems cooperate in the light reactions: – The water-splitting photosystem – The NADPH-producing photosystem
- 27. © 2010 Pearson Education, Inc. • The light reactions are located in the thylakoid membrane.
- 28. © 2010 Pearson Education, Inc. • An electron transport chain: – Connects the two photosystems – Releases energy that the chloroplast uses to make ATP
- 29. Light H2O Thylakoid membrane 2e– O2 ATP NADP Light Stroma Inside thylakoid Photosystem Photosystem Electron transport chain NADPH ADP P H+ ATP synthase To Calvin cycle H Electron flow H+ H H H H 1 2 Figure 7.11
- 30. Light H2O Thylakoid membrane 2e– O2 ATP NADP Light Stroma Inside thylakoid Photosystem Photosystem Electron transport chain NADPH ADP P ATP synthase To Calvin cycle Electron flow H 1 2 H H H H H H Figure 7.11a
- 31. Water-splitting photosystem e– ATP NADPH e– e– e– e– e– e– NADPH-producing photosystem Figure 7.12
- 32. THE CALVIN CYCLE: MAKING SUGAR FROM CARBON DIOXIDE • The Calvin cycle: – Functions like a sugar factory within the stroma of a chloroplast – Regenerates the starting material with each turn © 2010 Pearson Education, Inc.
- 33. Calvin cycle P P P Three-carbon moleculeRuBP sugar CO2 (from air) Figure 7.13-1
- 34. ATP NADPH Calvin cycle ADP P NADP P P P P G3P sugar Three-carbon moleculeRuBP sugar CO2 (from air) Figure 7.13-2
- 35. ATP NADPH ADP P NADP P P P P P P G3P sugar Three-carbon molecule G3P sugar G3P sugar RuBP sugar CO2 (from air) Calvin cycle Glucose (and other organic compounds) Figure 7.13-3
- 36. ATP NADPH Calvin cycle ADP P NADP P P P P P P ADP P ATP G3P sugar Three-carbon molecule G3P sugar G3P sugar RuBP sugar CO2 (from air) Glucose (and other organic compounds) Figure 7.13-4
- 37. Evolution Connection: Solar-Driven Evolution • C3 plants: – Use CO2 directly from the air – Are very common and widely distributed © 2010 Pearson Education, Inc.
- 38. © 2010 Pearson Education, Inc. • C4 plants: – Close their stomata to save water during hot and dry weather – Can still carry out photosynthesis • CAM plants: – Are adapted to very dry climates – Open their stomata only at night to conserve water
- 39. Sugar C4 Pathway (example: sugarcane) C4 plant Calvin cycle Cell type 1 Four-carbon compound Cell type 2 CO2 CO2 Figure 7.14a
- 40. CAM plant Sugar Calvin cycle Day Four-carbon compound Night CAM Pathway (example: pineapple) CO2 CO2 Figure 7.14b
- 41. Carbon dioxide 6 O26 CO2 6 H2O C6H12O6 Water Glucose Photo- synthesis Oxygen gas Light energy Figure 7.UN1
- 42. Light reactions CO2 O2 H2O (C6H12O6) NADPH Light Sugar ATP ADP P NADP Calvin cycle Figure 7.UN2
- 43. Light reactions CO2 O2 H2O (C6H12O6) NADPH Light Sugar ATP ADP P NADP Calvin cycle Figure 7.UN3
- 44. Carbon dioxide 6 O26 CO2 6 H2O C6H12O6 Water Glucose Photosynthesis Oxygen gas Light energy Figure 7.UN4
- 45. Light H2O O2 Chloroplast Light reactions NADPH ATP Calvin cycle CO2 NADP+ ADP P Sugar (C6H12O6) Stack of thylakoids Stroma Figure 7.UN5
- 47. NADPH Calvin cycle ADP P NADP P ATP G3P CO2 Glucose and other compounds Figure 7.UN7