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Photosynthesis

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Photosynthesis

  1. 1. Review Question• Which mode of nutrition do the green plants carry out?A. Autotrophic nutritionB. Heterotrophic nutrition
  2. 2. Sorry! You’re wrong!• Heterotrophic nutrition is the mode of nutrition in which organisms have to depend on other organisms or dead organic matters as their food sources. Green plants, however, can make organic food by themselves using simple inorganic substances. Back
  3. 3. Very Good!• Autotrophic nutrition is the mode of nutrition in which organisms can make organic food by themselves using simple inorganic substances.• The process by which the green plants obtain nutrients is called :- Photosynthesis
  4. 4. Overview of nutrition in green plantscarbon dioxide and water photosynthesiscarbohydrates (e.g. glucose) mineral salts (e.g. NO3-, SO42-) fatty acids glycerol amino acids water nutrients for plants can be used to produce all plant materials (e.g. enzymes, cell wall, cytoplasm, cell membrane, chlorophyll)
  5. 5. Nature of photosynthesis• Anabolic process• Takes place in chloroplast• Necessary factors :•Carbon dioxide•Water•Sunlight•Chlorophyll
  6. 6. Light
  7. 7. Light Absorption SpectrumWhy leave looked green?
  8. 8. Different pigments in absorption spectrum
  9. 9. How light energy used?
  10. 10. Light reaction• Light energy is trapped by chlorophyll in chloroplast
  11. 11. Light reactionLight energy absorbed by chlorophyll splits water molecules intohydrogen and oxygen
  12. 12. Light reactionOxygen is released as a gas through stoma to outside
  13. 13. Light reactionHydrogen is fed into dark reaction
  14. 14. Dark reaction• No light is required; can combines with CO2 to formHydrogen producedain light reactiontake place either inWater is formed as by-productcarbohydrates light or darkness
  15. 15. Chlorophyll Structure
  16. 16. Light ReactionPhotophosphorylation
  17. 17. Cyclic photophosphorylation
  18. 18. Dark Reaction M. Calvin
  19. 19. Calvin Cycle
  20. 20. CHLOROPLAST
  21. 21. Fate of product of photosynthesis Kreb cycle
  22. 22. Factors affect rate of photosynthesis
  23. 23. Expt. Show effect of factorsConc. Of DistanceNaHCO3 Heat
  24. 24. Fate of carbohydrate products in the plantcarbon dioxide and water photosynthesiscarbohydrates (e.g. glucose) mineral salts (e.g. NO3-, SO42-) fatty acids glycerol amino acids water
  25. 25. Fate of carbohydrate products in the plant carbon dioxide and water photosynthesiscarbohydrates (e.g. glucose) mineral salts (e.g. NO3-, SO42-) fatty acids glycerol amino acids waterrelease energy by respiration
  26. 26. Fate of carbohydrate products in the plant carbon dioxide and water photosynthesiscarbohydrates (e.g. glucose) mineral salts (e.g. NO3-, SO42-) fatty acids glycerol amino acids waterconvert into starch for storage
  27. 27. Fate of carbohydrate products in the plant carbon dioxide and water photosynthesiscarbohydrates (e.g. glucose) mineral salts (e.g. NO3-, SO42-) fatty acids glycerol amino acids waterchange into sucrose and is transportedto other parts through phloem
  28. 28. Fate of carbohydrate products in the plantcarbon dioxide and water photosynthesiscarbohydrates (e.g. glucose) mineral salts (e.g. NO3-, SO42-) fatty acids glycerol amino acids water combine to form fats and oils to form cell membranes and as a food store
  29. 29. Fate of carbohydrate products in the plantcarbon dioxide and water photosynthesiscarbohydrates (e.g. glucose) mineral salts (e.g. NO3-, SO42-) fatty acids glycerol amino acids water join together to become protein molecules
  30. 30. Mineral requirements in plants• In order to synthesize amino acids, nitrate ions must be taken into the plant from the soil through the root• Other minerals are also necessary to maintain the life of the plant
  31. 31. Expt. Show effect of mineralsDifferentNutrientadded
  32. 32. The importance of nitrogen• For synthesis of proteins, chlorophyll, etc.• Taken in the form of nitrate ions• Deficiency symptoms: – Little growth (no protein made) – Yellowing of leaves (chlorophyll made)
  33. 33. The importance of magnesium• Essential component of chlorophyll• Deficiency symptoms: – Yellowing of leaves (no chlorophyll made) – Poor growth (no food manufactured because of lack of chlorophyll)
  34. 34. Use of fertilizers in agriculture• Continuous harvesting crops removes the valuable mineral salts from soil ∴Fertilizers are added to replace such loss• Two kinds of fertilizers: – Natural fertilizers – Chemical fertilizers
  35. 35. Natural fertilizers• From manure• Organic compounds in it are decomposed by bacteria in soil to form mineral salts
  36. 36. Chemical fertilizers• Mainly nitrogenous and phosphorous compounds manufactured artificially
  37. 37. Comparison between natural and chemical fertilizersNatural fertilizers Chemical fertilizersVery cheap More expensiveContain humus which No humus so cannotcan improve soil improve soil texturetextureLess soluble in water Very soluble in waterso less likely to be so more likely to bewashed away washed away
  38. 38. Comparison between natural and chemical fertilizersNatural fertilizers Chemical fertilizersLess soluble in water Very soluble in waterso more difficult to be so easier to beabsorbed absorbedTime is needed for the More readily to bedecomposition to used by the plantscomplete beforenutrient is available toplants
  39. 39. Importance of photosynthesis• It is the only method to convert energy in sunlight into chemical energy – Animals have to depend on plants for food supply – Plants: producers; animals : consumers• To maintain a constant oxygen level in the atmosphere
  40. 40. Experiments to test for necessary factors of photosynthesis • Experimental set-up: To remove the factor under study and to see if photosynthesis still takes place • Control set-up: Identical to experimental set-up except that the missing factor is present
  41. 41. A set-up to study whether light is necessary for photosynthesisRegion BRegion A leafy shootwater
  42. 42. Which is the control, the exposed region A or the shaded region B?
  43. 43. What is the purpose of setting up region A? • As a control Too simple and not explicit!To show that photosynthesis cannot take place in the absence oflight
  44. 44. Destarching• Reason: – To avoid any existing starch in the leaves interfering with the result, and to show that any starch found after the experiment was produced during the period of investigation• Method: – By placing the plant in dark for at least 24 hours
  45. 45. Parts of plant where photosynthesis takes place• Places where chloroplasts are found• Mainly in the leaf because – it contains a lot of chloroplasts – it is well adapted for performing photosynthesis
  46. 46. Cross-section of a dicot leaf upper epidermis protect internal tissues from mechanical damage and bacterial and fungal invasion
  47. 47. Cross-section of a dicot leaf Cuticle • a waxy layer • prevent water loss from the leaf surface
  48. 48. Cross-section of a dicot leaf mesophyll
  49. 49. Cross-section of a dicot leaf palisade mesophyll columnarmany contains cells closely packed chloroplasts together ∴absorb light more efficiently
  50. 50. Cross-section of a dicot leaf irregular cells loosely packed together to leave numerous large air spaces →allow rapid diffusion of less chloroplasts gases for throughout the photosynthesis leaf spongy mesophyll
  51. 51. Cross-section of a dicot leaf same as upper epidermis except the cuticle is thinner lower epidermis
  52. 52. Cross-section of a dicot leaf stoma opening which allows gases to pass through it to go into or out of the leaf
  53. 53. Cross-section of a dicot leaf guard cells control the size of stoma
  54. 54. Cross-section of a dicot leaf vascular bundle (vein)
  55. 55. Cross-section of a dicot leaf xylem •to transport water and mineral salts towards the leaf
  56. 56. Cross-section of a dicot leaf phloem •to transport organic substances away from the leaf
  57. 57. Adaptation of leaf to photosynthesis Upper epidermis and cuticle is transparent Allows most light to pass to photosynthetic mesophyll tissues
  58. 58. Adaptation of leaf to photosynthesis Palisade mesophyll cells are closely packed and contain many chloroplasts To carry out photosynthesis more efficiently
  59. 59. Adaptation of leaf to photosynthesis Spongy mesophyll cells are loosely packed with numerous large air spaces To allow rapid diffusion of gases throughout the leaf
  60. 60. Adaptation of leaf to photosynthesis Numerous stomata on lower epidermis To allow rapid gaseous exchange with the atmosphere
  61. 61. Adaptation of leaf to photosynthesis Extensive vein system • Allow sufficient water to reach the cells in the leaf • To carry food away from them to other parts of the plant
  62. 62. CHEMOSYNTHSIS•Iron bacteria•Colorless sulphur bacteria•Nitrifying bacteria
  63. 63. Iron bacteria
  64. 64. Nitrifying bacteria

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