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Concept 8.1

Concept 8.1. PHOTOSYNTHESIS USES LIGHT ENERGY TO MAKE FOOD. PHOTOSYNTHESIS. Process that converts light energy to chemical energy Occurs in chloroplasts of green plants. CHLOROPLASTS. Most are located in leaves— major site of photosynthesis Contain pigment called chlorophyll

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Concept 8.1

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  1. Concept 8.1 PHOTOSYNTHESIS USES LIGHT ENERGY TO MAKE FOOD

  2. PHOTOSYNTHESIS • Process that converts light energy to chemical energy • Occurs in chloroplasts of green plants

  3. CHLOROPLASTS • Most are located in leaves— major site of photosynthesis • Contain pigment called chlorophyll • Gives chloroplasts their green color

  4. CHLOROPLAST STRUCTURE • Enclosed by two membranes • Inner membrane encloses a thick fluid calledstroma • Disk-shaped sacs calledthylakoids are suspended in stroma • Granum: stack of thylakoids

  5. CHLOROPLAST STRUCTURE

  6. PHOTOSYNTHESIS EQUATION sunlight • 6 CO2 + 6 H2O  C6H12O6 + 6 O2 sunlight 6 carbon dioxide + 6 water  glucose + 6 oxygen • Occurs in two main stages: 1. light reactions 2. Calvin cycle

  7. CHLOROPLAST STRUCTURE ORGANIZES PHOTOSYNTHESIS • Reactions take place in different areas of chloroplast: • Light reactions occur inthylakoidmembranes • Calvin cycle occurs in thestroma

  8. PHOTOSYNTHESIS OVERVIEW

  9. PHOTOSYNTHESIS and CELLULAR RESPIRATION • The two processes are linked: • photosynthesis: process by which plants use the sun’s energy to convert water and carbon dioxide into sugars • cellular respiration: chemical process that uses oxygen to convert chemical energy stored in food molecules to produce ATP

  10. PHOTOSYNTHESIS and CELLULAR RESPIRATION • Both processes recycle common set ofchemicals: • Water, carbon dioxide, oxygen, glucose • Products of photosynthesis are the ingredients for cellular respiration • Products of cellular respiration are the ingredients for photosynthesis

  11. PHOTOSYNTHESIS and CELLULAR RESPIRATION Photosynthesis Equation: sunlight 6CO2 + 6 H2O  C6H12O6 + 6 O2 sunlight 6 Carbon Dioxide + 6 Water  Glucose + 6 Oxygen Cellular Respiration Equation: C6H12O6 + 6 O2  6 CO2 + 6 H2O + ATP Glucose + 6 Oxygen  6 Carbon Dioxide + 6 Water

  12. PHOTOSYNTHESIS and CELLULAR RESPIRATION

  13. LIGHT REACTIONS • Convert energy in sunlight to chemical energy in steps • Chlorophyll molecules capture light energy (units called photons) • Captured energy is used to split water molecules photolysis • H2O  O2 and H+ ions produced

  14. LIGHT REACTIONS • O2 escapes from leaf as waste product • H+ bonds to NADP+ (electron carriermolecule) forming NADPH • NADPH moves to stroma • ATP is produced by light energy

  15. THE CALVIN CYCLE • Glucose made from atoms of CO2, hydrogen, ATP, and electrons carried by NADPH • Enzymes for Calvin cycle reactions are located outside thylakoids  dissolved in stroma • ATP from light reactions provides energy to make glucose

  16. THE CALVIN CYCLE • Calvin cycle reactions are also called the light-independent or darkreactions(can occur without direct light) • Cannot continue indefinitely without two inputs supplied by light reactions: • 1. ATP 2. NADPH

  17. Concept 8.2 THE LIGHT REACTIONS CONVERT LIGHT ENERGY TO CHEMICAL ENERGY

  18. LIGHT ENERGY & PIGMENTS • Visible light: part of the electromagnetic spectrum our eyes detect as different colors ROYGBIV • Pigments: chemicals that absorb, transmit, or reflect different wavelengths of light

  19. CHLOROPLAST PIGMENTS • Absorb blue-violet & red-orange light • Convert absorbed light energy to chemical energy • Do not absorb green light well: • reflect or transmit it back • makes leaves look green

  20. LIGHT REACTIONS & PHOTOSYSTEMS • Photosystems: clusters of chlorophyll and other molecules in thylakoid membranes of the chloroplast • Two photosystems involved in light reactions • Each photosystem uses a different chlorophyll molecule and performs a different task • Electron transport chain connects the two photosystems and produces ATP

  21. PHOTOSYSTEM 2 • “Water-splitting” photosystem • Produces hydrogen ions (H+) and releases oxygen (O2) as a waste product • Electrons released in splitting H2O are used to make ATP

  22. PHOTOSYSTEM 1 • “NADPH producing photosystem” • Light striking another chlorophyll molecule causes electrons to gain energy and leave the molecule • These electrons along with H+ ions from water are added to NADP+ to produce NADPH

  23. PHOTOSYSTEMS

  24. LIGHT REACTIONS - SUMMARY

  25. What you need to know about the light reactions • Occur on thylakoid membranes • Get energy from photons of light • Reactants: H2O, light • End products: O2, NADPH, ATP

  26. What you need to know about the light reactions • Destination of end products: • ATP and NADPH go to stroma (Calvin cycle) • O2 leaves as waste product

  27. Concept 8.3 THE CALVIN CYCLE MAKES SUGAR FROM CARBON DIOXIDE

  28. CALVIN CYCLE • Uses carbon dioxide and a 5-carbon sugar (RuBP) along with molecules from the light reactions (ATP & NADPH) to produce glucose—the main cellular fuel • Occurs in the stroma of chloroplast

  29. What you need to know about the Calvin cycle • What are the reactants? 1. RuBP 2. NADPH 3. ATP 4. CO2

  30. CALVIN CYCLE • Where do the reactants come from? - RuBP  present in stroma - CO2 from atmosphere - NADPH, ATP  from light reactions

  31. CALVIN CYCLE • What are the end products? - 3-carbon sugar G3P  used by plant cells to produce more complex carbohydrates - glucose - starch - cellulose

  32. CALVIN CYCLE • Where does energy for Calvin cycle come from? - ATP produced in light reactions • Where does the Calvin cycle occur? - stroma of chloroplast

  33. CALVIN CYCLE

  34. SUMMARY OF PHOTOSYNTHESIS

  35. SUMMARY OF PHOTOSYNTHESIS • 6 CO2 + 6 H2O  C6H12O6 + 6 O2 • LIGHT REACTIONS: • Occur on thylakoid membranes • Convert light energy to chemical energy of ATP • Use reactant H2O from the equation and releases product O2

  36. SUMMARY OF PHOTOSYNTHESIS • CALVIN CYCLE: • Occurs in stroma of chloroplast • Uses ATP and NADPH from light reactions • Uses the reactant CO2 from the equation and produces sugar

  37. Concept 8.4 PHOTOSYNTHESIS HAS A GLOBAL IMPACT

  38. THE CARBON CYCLE • Process by which carbon moves from inorganic to organic compounds and back • Photosynthesis converts inorganic carbon dioxide to organic compounds • Consumers eat producers and return carbon dioxide to the atmosphere via cellular respiration

  39. CARBON CYCLE

  40. PHOTOSYNTHESIS & GLOBAL CLIMATE • Photosynthesis uses CO2 to make sugars • Most organisms give off CO2 in cellular respiration • Total effect of all the organisms on Earth has a large effect on the amount of CO2 in the atmosphere

  41. GREENHOUSE EFFECT • Amount of CO2 in atmosphere has been increasing rapidly • greenhouse effect: CO2 traps heat from the sun that would otherwise escape into space • Increased CO2—mainly from fossil fuels—traps more heat leading to global warming

  42. GREENHOUSE EFFECT

  43. THE END

  44. THE CALVIN CYCLE

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