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Photosynthesis

Photosynthesis. Making Glucose. Photosynthesis. Where does all that glucose come from?. Trees From Rocks?. CO 2. CO 2. CO 2. CO 2. CO 2. CO 2. radiant energy. What is Photosynthesis?. Photosynthesis. glucose. What is Photosynthesis?.

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Photosynthesis

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  1. Photosynthesis Making Glucose

  2. Photosynthesis Where does all that glucose come from?

  3. Trees From Rocks?

  4. CO2 CO2 CO2 CO2 CO2 CO2 radiant energy What is Photosynthesis? Photosynthesis glucose

  5. What is Photosynthesis? In the process of photosynthesis, plants convert radiant energy from the sun into chemical energy in the form of glucose (sugar)

  6. An Overview

  7. Photosynthetic Organisms cyanobacteria protists plants

  8. That’s a lot of photosynthesis

  9. http://www.smhi.se/weather/baws_ext/info/2004/Baltic_algae_2004_en.htmhttp://www.smhi.se/weather/baws_ext/info/2004/Baltic_algae_2004_en.htm So is this!

  10. H+ H+ O2 H2O Energy glucose CO2 Photosynthesis CO2 + H2O + energy  glucose + O2

  11. H+ H+ O2 H2O Energy glucose CO2 • Although photosynthesis and cellular respiration appear to simply be reverse processes, they are not! • They use different mechanisms (enzymes) Cellular Respiration Photosynthesis glucose + O2 CO2 + H2O + energy

  12. Main Similarities • Use cytochrome complexes to generate a proton gradient in a double membraned organelle • Use ATP synthase • Use similar energy carriers eg. NADH vs NADPH

  13. cuticle epidermis palisade mesophyll spongy mesophyll vascular bundle stomate Recall: The Leaf Epidermis Mesophyll Vascular Bundles

  14. Where Does Photosynthesis Occur? CO2 O2 H2O

  15. Where Does Photosynthesis Occur? CO2 O2 H2O

  16. cell wall nucleus cytosol chloroplast

  17. cell wall nucleus cytosol chloroplast All photosynthetic reactions occur in the chloroplasts

  18. Outer membrane Inner membrane Stroma Thylakoid Granum The Chloroplast

  19. Stroma Lamella (connects grana) Thylakoid (contains chlorophyll) Thylakoid Space (Lumen) The Chloroplast

  20. some makes ATP glucose glucose NADPH PHOTOSYNTHESIS Stages of Photosynthesis • There are two main stages of photosynthesis: Light Reactions Dark Reactions makes

  21. some makes ATP glucose glucose NADPH PHOTOSYNTHESIS Stages of Photosynthesis • There are two main stages of photosynthesis DON’T BE FOOLED!! Both light and dark reactions occur during the day. The “Dark” reactions don’t REQUIRE light while the “Light” reactions do! Light Reactions Dark Reactions makes

  22. some makes ATP glucose glucose NADPH PHOTOSYNTHESIS Stages of Photosynthesis • There are two main stages of photosynthesis: Light Dependent Reactions Light Independent Reactions makes

  23. Light • The full range of wavelengths of light emitted from the sun is known as the electromagnetic spectrum • Visible light is between 400-700nm

  24. Particle And A Wave • Light travels as an electromagnetic wave of energy • It is possible to view light as traveling in bundles of energy called photons • Chlorophyll can absorb photons of particular wavelengths Photon Photon Photon Photon Photon

  25. What Happens to Photons?

  26. Chlorophyll • Chlorophyll is a pigment • This means it is a chemical that absorbs certain wavelengths of light • When chlorophyll absorbs light, its electrons may enter an excited state

  27. Chlorophyll a Chlorophyll b Capturing Light • The most common pigments in plants are chlorophyll a and chlorophyll b Absorbance: absorbed absorbed

  28. Chlorophyll a Chlorophyll b GREEN What do we see? Capturing Light • The most common pigments in plants are chlorophyll a and chlorophyll b Reflection: reflected

  29. Other Pigments • Though chlorophylls are the most common pigments used in photosynthesis, other pigments are used too in order to absorb at other wavelengths: egs • Carotenoids • Phycobilins • Xanthophylls

  30. Other Pigments

  31. Converting Radiant Energy to Chemical Energy • Chlorophyll in the thylakoid membrane excites its electrons using radiant energy • These energized electrons can then be transferred to a primary electron acceptor via redox reaction

  32. a Light Reactions(Light-Independent Reactions) • Protein complexes in the thylakoid membrane contain: • Antannae pigments: mostly chlorophyll b • Reaction Center: a molecule of chlorophyll a • A primary electron acceptor • These complexes are called photosystems Primary Electron Acceptor

  33. Light Reactions(Light-Independent Reactions) • The photosystems are known as • P700 or PSI • P680 or PSII • The numbers correspond to the wavelength at which their absorption spectrum peaks Thylakoid PS I P700 PS II P680

  34. a a a Light Reactions(Light-dependent Reactions) • Photons of light are absorbed by antenna pigments causing them to move from ground state to an excited state. • “Excitation” energy is passed along chlorophyll molecules until it reaches the reaction centre. • Chlorophyll ain the reaction centre absorbs the energy. • The high-energy state of chlorophyll a causes it to emit 2 electrons. • The primary electron acceptor takes the electrons from chlorophyll a. • this process is called photoexcitation P Thylakoid Electron Acceptor PS I PS II

  35. H+ H+ O2 H2O Non-Cyclic Electron Pathway High • Photosystem II aquires a supply of electrons by using the sun’s energy to hydrolyze water. • This is called photolysis. Energy H+ H+ H+ H+ H+ H+ H+ Low H+ H+ PS II Stroma Thylakoid P H+ H+ H+ Membrane H+ H+ H+ H+ H+ H+ H+ Thylakoid Lumen H+ H+ H+ H+ H+ H+

  36. O2 Non-Cyclic Electron Pathway High • Electrons are re-energized at photosystem I • The high energy electrons are involved in a redox reaction to generate the high energy NADPH molecule • The proton gradient is used to generate ATP through ATP Synthase • The reaction center passes electrons through an electron transport system containing a cytochrome complex (cytochrome b6f) • This complex generates a proton gradient Energy H+ H+ H+ H+ H+ H+ H+ Low H+ H+ ATP PS I E T C PS II Stroma Thylakoid P H+ Membrane H+ H+ H+ H+ H+ H+ H+ Thylakoid Lumen H+ H+ H+ H+ H+ H+ H+ H+

  37. Non-Cyclical Electron Pathway High Energy H+ NADP+ H+ H+ H+ ATP H+ H+ H+ Low H+ H+ NADPH PS I E T C PS II Stroma Thylakoid H+ Membrane H+ H+ H+ H+ H+ Thylakoid Lumen H+ H+ H+ H+ H+ H+ H+ H+ H+ H+

  38. The End Result • These end products of the light-dependent reactions can now be used to synthesize glucose ATP NADPH

  39. Cyclic Electron Pathway High • Simple organisms like bacteria are able to meet their energy demands by using PS I alone to generate ATP • In this way they generate cellular energy without synthesizing glucose. Energy H+ H+ H+ H+ H+ H+ H+ Low H+ H+ ATP PS I E T C P H+ Membrane H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+

  40. Cyclic Electron Pathway High Energy H+ H+ H+ H+ ATP H+ H+ H+ Low H+ H+ ATP PS I E T C P H+ Membrane H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+

  41. The Dark Reaction

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