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PHOTOSYNTHESIS

PHOTOSYNTHESIS. 3.8 Standard Level 8.2 Additional Higher Level. 8.2.1 DRAW & LABEL a diagram showing the structure of a chloroplast as seen in electron micrographs. (a) Cell wall (b) Double membrane (c) Starch grain (d) Grana (e) Thylakoid (f) Stroma.

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PHOTOSYNTHESIS

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  1. PHOTOSYNTHESIS 3.8 Standard Level 8.2 Additional Higher Level

  2. 8.2.1 DRAW & LABEL a diagram showing the structure of a chloroplast as seen in electron micrographs. (a) Cell wall (b) Double membrane (c) Starch grain (d) Grana (e) Thylakoid (f) Stroma

  3. 3.8.1 State that photosynthesis involves the conversion of light energy into chemical energy. • Need carbon dioxide, water, w/light and chlorophyll... •  glucose and oxygen

  4. 3.8.2 State that light from the Sun is composed of a range of wavelengths (colors). • Sunlight = white light (all colors, λ)

  5. 3.8.4 Outline the differences in absorption of red, blue, and green light by chlorophyll. • Shine white light through a chlorophyll solution • Some absorbed, some not • absorption spectrum • Orange-red & blue mostly absorbed • Green mostly reflected/transmitted

  6. 8.2.7 Explain the relationship between the action spectrum and the absorption spectrum of photosynthetic pigments in green plants. Not all wavelengths are equally used in photosynthesis Action spectrum shows how well used Blue, red are peaks for absorption & action b/c rate of photosynth Low abs green b/c reflection from chlorophyll...green appearance

  7. 3.8.3 State that chlorophyll is the main photosynthetic pigment. • Green, reflects green light & absorbs all others • Several (chl a, chl b ,etc) • Each has own absorption spectrum

  8. 3.8.5 State that light energy is used to produce ATP, and to split water molecules (photolysis) to form oxygen and hydrogen. • Light dependent reactions

  9. 8.2.2 State that photosynthesis consists of light-dependent and light-independent reactions. • light-dependent reactions • NEED light • On thylakoid membrane • light-independent reactions • Any time, depending on reactants (ATP and NADPH from light-dependent) • In stroma

  10. 8.2.3 Explain the light-dependent reactions. • Use light energy • Split water • H+, e- • Produce ATP, NADPH (go to light-indep rxns) • O2 = waste, leaves chloroplast • Thylakoid membrane • Non-cyclic photophosphorylation • Cyclic photophosphorylation

  11. 8.2.3 Explain the light-dependent reactions. • Cyclic photophosphorylation • E- go to 2nd e- acceptor, but don’t produce NADPH • Instead, go thru membrane, ETC, redox rxns, returned to PSI • PSII not involved • Doesn’t produce NADPH • Doesn’t drive Calvin Cycle • Won’t produce carbs for energy storage • Does produce ATP

  12. 8.2.3 Explain the light-dependent reactions. • Non-cyclic photophosphorylation • Light absorbed by PSII (grana) • Excites e- • (higher energy level, move away from nucleus) (“photoactivation of PSII”) • E- taken up by e-acceptor • Chl a gets + charge • several e-carriers in membrane (redox rxns), to PSI (ETC) • Photolysis: Chl a+ induces lysis of water • Light also absorbed in PSI, photoactivation of PSI; • different e- acceptor, passed on, • taken up by NADP+ • Reduced to NADPH • Chl a+ of PSI receives e- from ETC (from PSII) & becomes uncharged

  13. 8.2.4 Explain photophosphorylation in terms of chemiosmosis. • E- from photolysis taken up by Chl a+ (PSII) • Chl a+  Chl a • Oxygen released (waste) • H+ pumped to inside grana, accumulate (thyl space), conc gradient • ATP synthase: phosphorylation of ADP + P  ATP • “photophosphorylation” b/c light involved

  14. e-

  15. 3.8.6 State that ATP and hydrogen (derived from the photolysis of water) are used to fix carbon dioxide to make organic molecules. Light-independent reactions ATP High energy bonds between P groups Reversible

  16. 8.2.5 Explain the light-independent reactions. • ATP, NADPH, H+ from lt-dep rxns • Calvin Cycle • Combine 3 CO2s into 1 triose phosphate (3C) • 2 of these combine to form glucose (6C) • Stroma

  17. 8.2.5 Explain the light-independent reactions. • RuBP: CO2 acceptor • RuBP carboxylase: Rubisco (catalyst) • Takes up CO2, forms GP (G3P) • GP reduced to TP but needs energy from ATP and reducing power from NADPH • TP converted to glucose, sucrose, starch, fatty acids, amino acids, ... • RuBP regenerated (use ATP) to keep it going

  18. 3.8.7 Explain that the rate of photosynthesis can be measured directly by the production of oxygen or the uptake of carbon dioxide, or indirectly by an increase in biomass. • Production of oxygen • Enclosed/controlled expt • Shine bright light on water plant • Measure oxygen in water • Uptake of carbon dioxide • Enclosed/controlled expt • Measure CO2 before/after or pH of water • Increase in biomass • Change in organic matter, not water • Indirect measurement of photosynth. • Dehydrate the plant before massing

  19. 3.8.8 Outline the effects of temperature, light intensity, and carbon dioxide concentration on the rate of photosynthesis. Temperature: • Optimal ranges for enzymes • Kinetic energy of reactants • denaturation [Carbon dioxide]: • Reactant (like [substrate]) • Saturation level = max rate • Shaded on graph Light intensity: • Increases, rate increases • Too high can damage chlorophyll

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