Photosynthesis Life Is Solar Powered!

1. PhotosynthesisLife Is Solar Powered!

2. What Would Plants Look Like On Alien Planets? Why?

3. Why Would They Look Different? • Different Stars Give off Different types of light or Electromagnetic Waves • The color of plants depends on the spectrum of the star’s light, which astronomers can easily observe. (Our Sun is a type “G” star.)

4. Anatomy of a Wave • Wavelength • Is the distance between the crests of waves • Determines the type of electromagnetic energy

6. Electromagnetic Spectrum • Is the entire range of electromagnetic energy, or radiation • The longer the wavelength the lower the energy associated with the wave.

7. Visible Light • Light is a form of electromagnetic energy, which travels in waves • When white light passes through a prism the individual wavelengths are separated out.

8. Visible Light Spectrum • Light travels in waves • Light is a form of radiant energy • Radiant energy is made of tiny packets of energy called photons • The red end of the spectrum has the lowest energy (longer wavelength) while the blue end is the highest energy (shorter wavelength). • The order of visible light is ROY-G-BIV • This is the same order you will see in a rainbow b/c water droplets in the air act as tiny prisms

9. Light Reflected Light Chloroplast Absorbed light Granum Transmitted light Figure 10.7 Light Options When It Strikes A Leaf • Reflect – a small amount of light is reflected off of the leaf. Most leaves reflect the color green, which means that it absorbs all of the other colors or wavelengths. • Absorbed – most of the light is absorbed by plants providing the energy needed for the production of Glucose (photosynthesis) • Transmitted – some light passes through the leaf

11. Photosynthesis Overview Concept Map Photosynthesis includes Light independent reactions Light dependent reactions occurs in uses uses occur in Light Energy Thylakoid membranes ATP Stroma NADPH to produce to produce of ATP NADPH O2 Chloroplasts Glucose

12. Leaf cross section Vein Mesophyll CO2 O2 Stomata Figure 10.3 Anatomy of a Leaf

14. Chloroplast

15. Mesophyll Chloroplast 5 µm Outer membrane Intermembrane space Thylakoid Thylakoid space Granum Stroma Inner membrane 1 µm Chloroplast • Are located within the palisade layer of the leaf • Stacks of membrane sacs called Thylakoids • Contain pigments on the surface • Pigments absorb certain wavelenghts of light • A Stack of Thylakoids is called a Granum

16. Pigments • Are molecules that absorb light • Chlorophyll, a green pigment, is the primary absorber for photosynthesis • There are two types of cholorophyll • Chlorophyll a • Chlorophyll b • Carotenoids, yellow & orange pigments, are those that produce fall colors. Lots of Vitamin A for your eyes! • Chlorophyll is so abundant that the other pigments are not visible so the plant is green…Then why do leaves change color in the fall?

17. Color Change • In the fall when the temperature drops plants stop making Chrlorophyll and the Carotenoids and other pigments are left over (that’s why leaves change color in the fall).

18. Three different experiments helped reveal which wavelengths of light are photosynthetically important. The results are shown below. EXPERIMENT RESULTS Chlorophyll a Chlorophyll b Absorption of light by chloroplast pigments Carotenoids Wavelength of light (nm) (a) Absorption spectra. The three curves show the wavelengths of light best absorbed by three types of chloroplast pigments. Figure 10.9 • The absorption spectra of three types of pigments in chloroplasts

19. Rate of photosynthesis (measured by O2 release) (b) 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. • The action spectrum of a pigment • Profiles the relative effectiveness of different wavelengths of radiation in driving photosynthesis

20. Aerobic bacteria Filament of alga 500 600 700 400 (c) 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 O2 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. Light in the violet-blue and red portions of the spectrum are most effective in driving photosynthesis. CONCLUSION • The action spectrum for photosynthesis • Was first demonstrated by Theodor W. Engelmann

21. CH3 in chlorophyll a in chlorophyll b CHO CH2 CH3 CH H C C C Porphyrin ring: Light-absorbing “head” of molecule note magnesium atom at center C C CH3 C C H3C CH2 C N C N H C C Mg H N C C N H3C C C CH3 C C C C C H H CH2 H C C O CH2 O O C O O CH3 CH2 Hydrocarbon tail: interacts with hydrophobic regions of proteins inside thylakoid membranes of chloroplasts: H atoms not shown Figure 10.10 Chlorophyll • Chlorophyll a • Is the main photosynthetic pigment • Chlorophyll b • Is an accessory pigment

22. PHOTOSYNTHESIS • Comes from Greek Word “photo” meaning “Light” and “syntithenai” meaning “to put together” • Photosynthesis puts together sugar molecules using water, carbon dioxide, & energy from light.

23. Happens in two phases • Light-Dependent Reaction • Converts light energy into chemical energy • Light-Independent Reaction • Produces simple sugars (glucose) • General Equation • 6 CO2 + 12 H2O + light energy  C6H12O6 + 6 O2 + 6 H2O

24. First Phase • Requires Light = Light Dependent Reaction • Sun’s energy energizes an electron in chlorophyll molecule • Electron is passed to nearby protein molecules in the thylakoid membrane of the chloroplast

25. Excited state e– Heat Energy of election Photon (fluorescence) Ground state Chlorophyll molecule Photon Figure 10.11 A Excitation of Chlorophyll by Light • When a pigment absorbs light • It goes from a ground state to an excited state, which is unstable

26. Figure 10.11 B • If an isolated solution of chlorophyll is illuminated • It will fluoresce, giving off light and heat

27. ETC • Electron from Chlorophyll is passed from protein to protein along an Electron Transport Chain • Electrons lose energy (energy changes form) • Finally bonded with electron carrier called NADP+ to form NADPH or ATP • Energy is stored for later use

28. Two Photosystems • Photosystem II: Clusters of pigments boost e- by absorbing light w/ wavelength of ~680 nm • Photosystem I: Clusters boost e- by absorbing light w/ wavelength of ~760 nm. • Reaction Center: Both PS have it. Energy is passed to a special Chlorophyll a molecule which boosts an e-

29. e– ATP e– e– NADPH e– e– e– Mill makes ATP Photon e– Photon Photosystem I Photosystem II Figure 10.14  • A mechanical analogy for the light reactions

30. Thylakoid Photosystem Photon STROMA Light-harvesting complexes Reaction center Primary election acceptor e– Thylakoid membrane Special chlorophyll a molecules Transfer of energy Pigment molecules THYLAKOID SPACE (INTERIOR OF THYLAKOID) Figure 10.12 Photosystem • A photosystem • Is composed of a reaction center surrounded by a number of light-harvesting complexes

31. Where those electrons come from • Water • Electrons from the splitting of water (photolysis) supply the chlorophyll molecules with the electrons they need • The left over oxygen is given off as gas

32. Reactants: 12 H2O 6 CO2 6 H2O 6 O2 C6H12O6 Products: Figure 10.4 The Splitting of Water • Chloroplasts split water into • Hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules

33. High Quality H2O • Photolysis – Splitting of water with light energy • Hydrogen ions (H+) from water are used to power ATP formation with the electrons • Hydrogen ions (charged particle) actually move from one side of the thylakoid membrane to the other • Chemiosmosis – Coupling the movement of Hydrogen Ions to ATP production

34. Animation – takes a min. to load…be patient • Animation II – Does not take as long to load but it is not as good

35. H2O CO2 LIGHT NADP+ ADP CALVIN CYCLE LIGHT REACTOR ATP NADPH STROMA (Low H+ concentration) O2 [CH2O] (sugar) Cytochrome complex Photosystem II Photosystem I NADP+ reductase Light 2 H+ 3 NADP+ + 2H+ Fd NADPH + H+ Pq Pc 2 H2O 1⁄2 O2 THYLAKOID SPACE (High H+ concentration) 1 2 H+ +2 H+ To Calvin cycle ATP synthase Thylakoid membrane STROMA (Low H+ concentration) ADP ATP P H+ Figure 10.17 • The light reactions and chemiosmosis: the organization of the thylakoid membrane

36. Vocabulary Review • Light-Dependent • Pigment • Chlorophyll • Electron Transport Chain • ATP • NADPH • Photolysis • Chemiosmosis

37. e– ATP e– e– NADPH e– e– e– Mill makes ATP Photon e– Photon Photosystem I Photosystem II Figure 10.14  Light-Dependent • Converts light into chemical energy (ATP & NADPH are the chemical products). Oxygen is a by-product

38. Pigment • Molecules that absorb specific wavelengths of light • Chlorophyll absorbs reds & blues and reflects green • Xanthophyll absorbs red, blues, greens & reflects yellow • Carotenoids reflect orange

39. Chlorophyll • Green pigment in plants • Traps sun’s energy • Sunlight energizes electron in chlorophyll

40. Electron Transport Chain • Series of Proteins embedded in a membrane that transports electrons to an electron carrier

41. ATP • Adenosine Triphosphate • Stores energy in high energy bonds between phosphates

42. NADPH • Made from NADP+; electrons and hydrogen ions • Made during light reaction • Stores high energy electrons for use during light-Independent reaction (Calvin Cycle)

43. Chemiosmosis • The combination of moving hydrogen ions across a membrane to make ATP

44. H2O CO2 Light NADP  ADP + P LIGHT REACTIONS CALVIN CYCLE ATP NADPH Chloroplast [CH2O] (sugar) O2 Figure 10.5

45. PART II • LIGHT INDEPENDENT REACTION • Also called the Calvin Cycle • No Light Required • Takes place in the stroma of the chloroplast • Takes carbon dioxide & converts into sugar • It is a cycle because it ends with a chemical used in the first step • Calvin Cycle uses ATP & NADPH to make Glucose (C6H12O6)

46. Begins & Ends • The Calvin Cycle begins and ends with RuBP • CO2 is added to RuBP; “fixing” the CO2 in a compound • One compound made along the way is PGAL • PGAL can be made into sugars or RuBP • Calvin Cycle uses ATP & NADPH

47. H2O Input CO2 Light 3 (Entering one at a time) NADP+ CO2 ADP CALVINCYCLE LIGHTREACTION ATP NADPH Rubisco O2 [CH2O] (sugar) 3 P P Short-livedintermediate P 6 3 P P Ribulose bisphosphate(RuBP) 3-Phosphoglycerate 6 ATP 6 ADP CALVIN CYCLE 3 ADP 6 P P 3 ATP 1,3-Bisphoglycerate 6 NADPH 6 NADPH+ 6 P P 5 (G3P) 6 P Glyceraldehyde-3-phosphate (G3P) P 1 Glucose andother organiccompounds G3P(a sugar)Output Figure 10.18 • The Calvin cycle Phase 1: Carbon fixation Phase 3:Regeneration ofthe CO2 acceptor(RuBP) Phase 2:Reduction

48. Chloroplast – Where the Magic Happens! + H2O CO2 Energy ATP and NADPH2 Which splits water Light is Adsorbed By Chlorophyll Calvin Cycle ADP NADP Chloroplast Used Energy and is recycled. O2 + C6H12O6 Light Reaction Dark Reaction 6 CO2 + 12 H2O + Light energy  C6H12O6 + 6 O2 + 6 H2 O