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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ch. 10 Photosynthesis.

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Presentation on theme: "Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ch. 10 Photosynthesis."— Presentation transcript:

1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ch. 10 Photosynthesis

2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photosynthesis Energy flows into ecosystem as sunlight, Feeds the Biosphere Converts solar E into chemical E Light energy ECOSYSTEM CO 2 + H 2 O Photosynthesis in chloroplasts Cellular respiration in mitochondria Organic molecules + O 2 ATP powers most cellular work Heat energy Figure 9.2

3 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Energy Transformations Photoautotrophs (producers) – Use E of sunlight to make organic molecules from water and CO 2 (a) Plants (b) Multicellular algae (c) Unicellular protist 10 m 40 m (d) Cyanobacteria 1.5 m (e) Pruple sulfur bacteria Figure 10.2

4 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photosynthesis converts light E to the chemical E of food

5 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Heterotrophs Obtain organic material f/ other organisms Consumers of the biosphere

6 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chloroplasts: Site of Photosynthesis (plants) Leaf Vein Leaf cross section Figure 10.3 Mesophyll CO 2 O2O2 Stomata

7 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Leaf Anatomy

8 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chloroplasts Chloroplast Structure – Contain grana which consisting of thylakoid stacks Chloroplast Mesophyll 5 µm Outer membrane Intermembrane space Inner membrane Thylakoid space Thylakoid Granum Stroma 1 µm

9 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chloroplasts

10 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photosynthesis summary reaction 6 CO 2 + 12 H 2 O + Light energy C 6 H 12 O 6 + 6 O 2 + 6 H 2 O

11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chloroplasts split water into H 2 and O 2, incorporating the e - of H 2 into sugar molecules 6 CO 2 12 H 2 O Reactants: Products: C 6 H 12 O 6 6H2O6H2O 6O26O2 Figure 10.4

12 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photosynthesis as a Redox Process Water is oxidized, CO 2 is reduced Protons and Electron are taken from water and added to CO 2

13 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Two Stages of Photosynthesis: A Preview Light Reactions – Occurs on thylakoid membranes – Converts solar E to chemical E Dark Reaction (Calvin Cycle) – Occurs in the stroma – Forms sugar from carbon dioxide, using ATP for energy and NADPH for reducing power

14 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview of photosynthesis H2OH2O CO 2 Light LIGHT REACTIONS CALVIN CYCLE Chloroplast [CH 2 O] (sugar) NADPH NADP ADP + P O2O2 Figure 10.5 ATP

15 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lets Talk about Light Form of electromagnetic E, travels in waves

16 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Wavelength ( ) Distance between the crests of waves Determines the type of electromagnetic E More Powerful

17 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Electromagnetic spectrum Entire range of electromagnetic E, or radiation Gamma rays X-raysUVInfrared Micro- waves Radio waves 10 –5 nm 10 –3 nm 1 nm 10 3 nm 10 6 nm 1 m 10 6 nm 10 3 m 380450500550600650700750 nm Visible light Shorter wavelength Higher energy Longer wavelength Lower energy

18 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Visible light spectrum – Colors of light we can see – s that drive photosynthesis

19 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photosynthetic Pigments: The Light Receptors Substances that absorb visible light

20 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pigments Reflect light, which include the colors we see Light Reflected Light Chloroplast Absorbed light Granum Transmitted light Figure 10.7

21 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Transmitted vs. Absorbed Light Figure 10.8 White light Refracting prism Chlorophyll solution Photoelectric tube Galvanometer Slit moves to pass light of selected wavelength Green light The high transmittance (low absorption) reading indicates that chlorophyll absorbs very little green light. The low transmittance (high absorption) reading chlorophyll absorbs most blue light. Blue light 1 2 3 4 0 100 0

22 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Absorption spectra of 3 types of pigments Absorption of light by chloroplast pigments Chlorophyll a Wavelength of light (nm) Chlorophyll b Carotenoids

23 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Action spectrum of a pigment Effectiveness of different of radiation in driving photosynthesis Rate of photosynthesis (measured by O 2 release) Action spectrum. This graph plots the rate of photosynthesis versus wavelength. The resulting action spectrum resembles the absorption spectrum for chlorophyll a but does not match exactly (see part a). This is partly due to the absorption of light by accessory pigments such as chlorophyll b and carotenoids. (b)

24 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings First demonstrated by Theodor W. Engelmann 400 500600700 Aerobic bacteria Filament of alga Engelmanns experiment. In 1883, Theodor W. Engelmann illuminated a filamentous alga with light that had been passed through a prism, exposing different segments of the alga to different wavelengths. He used aerobic bacteria, which concentrate near an oxygen source, to determine which segments of the alga were releasing the most O 2 and thus photosynthesizing most. Bacteria congregated in greatest numbers around the parts of the alga illuminated with violet-blue or red light. Notice the close match of the bacterial distribution to the action spectrum in part b. (c) Light in the violet-blue and red portions of the spectrum are most effective in driving photosynthesis. CONCLUSION

25 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

26 Chlorophylls: Photosynthetic Pigments Chlorophyll a – Main photosynthetic pigment Chlorophyll b – Accessory pigment C CH CH 2 C C C C C CN N C H3CH3C C C C C C C C C N C C C C N Mg H H3CH3C H C CH 2 CH 3 H C H H CH 2 H CH 3 C O O O O O CHO in chlorophyll a in chlorophyll b Porphyrin ring: Light-absorbing head of molecule note magnesium atom at center Hydrocarbon tail: interacts with hydrophobic regions of proteins inside thylakoid membranes of chloroplasts: H atoms not shown Figure 10.10

27 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Assesory proteins Other accessory pigments – Absorb different s of light and pass the E to chlorophyll a

28 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Excitation of Chlorophyll by Light When a pigment absorbs light electrons go from their ground state to an excited state (unstable) Excited state Energy of election Heat Photon (fluorescence) Chlorophyll molecule Ground state Photon e–e– Figure 10.11 A

29 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photosystems I and II Mill makes ATP e–e– e–e– e–e– e–e– e–e– Photon Photosystem II Photosystem I e–e– e–e– NADPH Photon

30 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Starter Question Compare and contrast the electron transport chain in cellular respiration with the light reactions in photosynthesis. Be sure to indicate similarities and differences

31 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photosystem II and I: Site of Photophosphorylation Proton Motive Force? Non Cyclic Flow to Calvin Cycle

32 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chemiosmosis in Chloroplasts v. Mitochondria Spatial organization of chemiosmosis Key Higher [H + ] Lower [H + ] Mitochondrion Chloroplast MITOCHONDRION STRUCTURE Intermembrance space Membrance Matrix Electron transport chain H+H+ Diffusion Thylakoid space Stroma ATP H+H+ P ADP+ ATP Synthase CHLOROPLAST STRUCTURE Figure 10.16

33 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Light reactions and chemiosmosis: Cyclic Flow LIGHT REACTOR NADP + ADP ATP NADPH CALVIN CYCLE [CH 2 O] (sugar) STROMA (Low H + concentration) Photosystem II LIGHT H2OH2O CO 2 Cytochrome complex O2O2 H2OH2O O2O2 1 1 2 2 Photosystem I Light THYLAKOID SPACE (High H + concentration) STROMA (Low H + concentration) Thylakoid membrane ATP synthase Pq Pc Fd NADP + reductase NADPH + H + NADP + + 2H + To Calvin cycle ADP P ATP 3 H+H+ 2 H + +2 H + 2 H + NADPH and O2 Not produce. Does not go to Calvin Cycle

34 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

35 Calvin cycle Uses ATP and NADPH to convert CO 2 to sugar Similar to the citric acid cycle Occurs in the stroma

36 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Calvin Cycle Happens in the Stroma

37 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Other Calvin Cycle Calvin cycle (G3P) Input (Entering one at a time) CO 2 3 Rubisco Short-lived intermediate 3 PP P Ribulose bisphosphate (RuBP) P 3-Phosphoglycerate P6 P 6 1,3-Bisphoglycerate 6 NADPH 6 NADPH + 6 P P 6 Glyceraldehyde-3-phosphate (G3P) 6 ATP 3 ATP 3 ADP CALVIN CYCLE P 5 P 1 G3P (a sugar) Output Light H2OH2O CO 2 LIGHT REACTION ATP NADPH NADP + ADP [CH 2 O] (sugar) CALVIN CYCLE O2O2 6 ADP Glucose and other organic compounds Phase 1: Carbon fixation Phase 2: Reduction Phase 3: Regeneration of the CO 2 acceptor (RuBP) From Light Reactions From Light Reactions Glyceraldehyde-3-P Can go to sugars, amino acids, fatty acids

38 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Alternative mechanisms of carbon fixation have evolved in hot, arid climates

39 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings On hot, dry days, plants close their stomata – Conserving water but limiting access to CO 2 – Causing O 2 to build up photorespiration

40 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photorespiration: An Evolutionary Relic? Photosynthetic rate is reduced

41 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings C 4 Plants (e.g. corn) Minimize photorespiration – Incorporate CO 2 into four carbon compounds in mesophyll cells

42 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4 carbon compounds in bundle sheath cells release CO 2 CO 2 Calvin cycle

43 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings C 4 leaf anatomy and the C 4 pathway CO 2 Mesophyll cell Bundle- sheath cell Vein (vascular tissue) Photosynthetic cells of C 4 plant leaf Stoma Mesophyll cell C 4 leaf anatomy PEP carboxylase Oxaloacetate (4 C) PEP (3 C) Malate (4 C) ADP ATP Bundle- Sheath cell CO 2 Pyruate (3 C) CALVIN CYCLE Sugar Vascular tissue Figure 10.19 CO 2

44 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CAM Plants (e.g. pineapple) Open their stomata at night, CO 2 organic acids

45 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings During the day, stomata close – CO 2 is released from the organic acids for use in the Calvin cycle

46 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CAM pathway is similar to the C 4 pathway Spatial separation of steps. In C 4 plants, carbon fixation and the Calvin cycle occur in different types of cells. (a) Temporal separation of steps. In CAM plants, carbon fixation and the Calvin cycle occur in the same cells at different times. (b) Pineapple Sugarcane Bundle- sheath cell Mesophyll Cell Organic acid CALVIN CYCLE Sugar CO 2 Organic acid CALVIN CYCLE Sugar C4C4 CAM CO 2 incorporated into four-carbon organic acids (carbon fixation) Night Day 1 2 Organic acids release CO 2 to Calvin cycle Figure 10.20

47 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Review Light reactions: Are carried out by molecules in the thylakoid membranes Convert light energy to the chemical energy of ATP and NADPH Split H 2 O and release O 2 to the atmosphere Calvin cycle reactions: Take place in the stroma Use ATP and NADPH to convert CO 2 to the sugar G3P Return ADP, inorganic phosphate, and NADP+ to the light reactions O2O2 CO 2 H2OH2O Light Light reaction Calvin cycle NADP + ADP ATP NADPH + P 1 RuBP 3-Phosphoglycerate Amino acids Fatty acids Starch (storage) Sucrose (export) G3P Photosystem II Electron transport chain Photosystem I Chloroplast Figure 10.21

48 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Organic compounds produced by photosynthesis – Provide the E and building material for ecosystems

49 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Extra stuff: Light energy causes the removal of an electron from a molecule of P680 that is part of Photosystem II. The P680 requires an electron, which is taken from a water molecule, breaking the water into H + ions and O -2 ions. These O -2 ions combine to form the diatomic O 2 that is released.

50 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings


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