Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint TextEdit Art Slides for Biology, Seventh Edition Neil Campbell and Jane Reece Chapter 10 Photosynthesis
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10.1 Sunlight consists of a spectrum of colors, visible here in a rainbow
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10.2 Photoautotrophs (a) Plants (b) Multicellular algae (c) Unicellular protist 10 m 40 m (c) Cyanobacteria 1.5 m (d) Pruple sulfur bacteria These organisms use light energy to drive the synthesis of organic molecules from carbon dioxide and (in most cases) water. They feed not only themselves, but the entire living world. (a) On land, plants are the predominant producers of food. In aquatic environments, photosynthetic organisms include (b) multicellular algae, such as this kelp; (c) some unicellular protists, such as Euglena; (d) the prokaryotes called cyanobacteria; and (e) other photosynthetic prokaryotes, such as these purple sulfur bacteria, which produce sulfur (spherical globules) (c, d, e: LMs).
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10.3 Focusing in on the location of photosynthesis in a plant Mesophyll cell Mesophyll Vein Stomata CO 2 O2O2 Chloroplast 5 µm 1 µm Outer membrane Intermembrane space Inner membrane ThylakoidThylakoid Space Granum Stroma Leaf cross section
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10.4 Tracking atoms through photosynthesis 6 CO 2 12 H 2 O Reactants: Products: C 6 H 12 O 6 6H2O6H2O 6O26O2
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CO 2 CALVIN CYCLE O2O2 [CH 2 O] (sugar) NADP ADP + P i Figure 10.5 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle H2OH2O Light LIGHT REACTIONS Chloroplast ATP NADPH
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10.6 The electromagnetic spectrum 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 nm Visible light Shorter wavelength Higher energy Longer wavelength Lower energy
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10.7 Why leaves are green: interaction of light with chloroplasts Light Reflected Light Chloroplast Absorbed light Granum Transmitted light
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings TECNIQUE A spectrophotometer measures the relative amounts of light of different wavelengths absorbed and transmitted by a pigment solution. 2 The transmitted light strikes a photoelectric tube, which converts the light energy to electricity. 3 4 The electrical current is measured by a galvanometer. The meter indicates the fraction of light transmitted through the sample, from which we can determine the amount of light absorbed. White light is separated into colors (wavelengths) by a prism. 1 One by one, the different colors of light are passed through the sample (chlorophyll in this example). Green light and blue light are shown here. APPLICATION An absorption spectrum is a visual representation of how well a particular pigment absorbs different wavelengths of visible light. Absorption spectra of various chloroplast pigments help scientists decipher each pigment’s role in a plant. Figure 10.8 Research Method Determining an Absorption Spectrum
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings See Figure 10.9a for absorption spectra of three types of chloroplast pigments. Result 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 indicates that chlorophyll absorbs most blue light. Blue light
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10.9 Inquiry Which wavelengths of light are most effective in driving photosynthesis? Three different experiments helped reveal which wavelengths of light are photosynthetically important. The results are shown below. EXPERIMENT RESULTS Absorption of light by chloroplast pigments Chlorophyll a Chlorophyll b Carotenoids (a) Absorption spectra. The three curves show the wavelengths of light best absorbed by three types of chloroplast pigments. Wavelength of light (nm)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Aerobic bacteria Filament of alga Engelmann‘s 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Structure of chlorophyll molecules in chloroplasts of plants C CH CH 2 C C C C C C N 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Excitation of isolated chlorophyll by light Excited state Energy of election e–e– Heat Photon (fluorescence) Chlorophyll molecule Ground state Photon (a) Excitation of isolated chlorophyll molecule (b) Fluorescence
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings e–e– Figure How a photosystem harvests light Primary election acceptor Photon Thylakoid Light-harvesting complexes Reaction center Photosystem STROMA Thylakoid membrane Transfer of energy Special chlorophyll a molecules Pigment molecules THYLAKOID SPACE (INTERIOR OF THYLAKOID)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure How noncyclic electron flow during the light reactions generates ATP and NADPH P700 + CO 2 Photosystem II (PS II) H2OH2O Light LIGHT REACTIONS CALVIN CYCLE O2O2 NADPH [CH 2 O] (sugar) ee Primary acceptor 2 H + 1⁄21⁄2 H2OH2O ee ee 1 Energy of electrons Pq Cytochrome complex Pc ATP Electron transport chain NADP + Primary acceptor ee Photosystem I (PS I) Light ADP ATP 5 Fd Electron Transport chain 7 NADP + reductase NADPH NADP H H P680 O2O2 ee ee
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure A mechanical analogy for the light reactions Mill makes ATP e–e– e–e– e–e– e–e– e–e– Photon Photosystem II Photosystem I e–e– e–e– NADPH Photon
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Cyclic electron flow Primary acceptor Pq Fd Cytochrome complex Pc Primary acceptor Fd NADP + reductase NADPH ATP Photosystem II (PS II) Photosystem I (PS I) NADP +
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Comparison of chemiosmosis in mitochondria and chloroplasts 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The light reactions and chemiosmosis: the organization of the thylakoid membrane 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 1⁄21⁄2 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 +
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The Calvin cycle (Entering one at a time) CO 2 3 Phase 1: Carbon fixation Rubisco Short-lived intermediate 3 P P P Ribulose bisphosphate (RuBP) P 3-Phosphoglycerate P 6 P 1,3-Bisphosphoglycerate 6 NADPH 6 NADP + 6 P i P 6 Glyceraldehyde-3-phosphate (G3P) Phase 2: Reduction 6 ATP 3 ATP 3 ADP CALVIN CYCLE P 5 Phase 3: Regeneration of the CO 2 acceptor (RuBP) P 1 G3P (a sugar) Output Glucose and other organic compounds G3P 6 ADP Light H2OH2O CO 2 LIGHT REACTIONS NADPH NADP + [CH 2 O] (sugar) CALVIN CYCLE Input ATP ADP O2O2 6
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 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 CO 2
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure C 4 and CAM photosynthesis compared Organic acids release CO 2 to Calvin cycle 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 CO 2
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure A review of photosynthesis 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 reactions 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