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Lower Secondary - Photosynthesis

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This presentation is tailored for the Lower Secondary Science syllabus in Singapore.

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Lower Secondary - Photosynthesis

  1. 1. This presentation was produced by the Sciencedepartment of Temasek Secondary School.Redistribution or reproduction of this resource isprohibited by copyright regulations. Thisresource should be used for educationalpurposes.
  2. 2. Photosynthesis
  3. 3. Overview1. What is photosynthesis?2. Testing the leaf for starch tosee if photosynthesis has takenplace.3. Conditions and factorsaffecting photosynthesis.4. Importance of photosynthesis.
  4. 4. Lesson objectivesAt the end of the lesson, you will beable to:1. define photosynthesis.2. classify the various factors ofphotosynthesis into either raw materialsor conditions required forphotosynthesis.3. state the word and chemical equation forphotosynthesis.
  5. 5. Plants make their ownfood! Food for plants:•Energy-rich substances calledcarbohydrates (sugars)
  6. 6. PhotosynthesisLight PutTogether
  7. 7. blue blackblue-blackRawmaterialsConditions
  8. 8. Water Carbon dioxideGlucose(Sugar)OxygenLight,Chlorophyll,Suitable temperature++WORD EQUATION FOR PHOTOSYNTHESIS
  9. 9. 6H2O 6CO2C6H12O6 6O2Light,Chlorophyll,Suitable temperature++CHEMICAL EQUATION FOR PHOTOSYNTHESIS
  10. 10. Process where light energy isabsorbed by chlorophyll andconverted to chemical energy,which is used to synthesiseglucose from water and carbondioxide, liberating oxygenduring the process.
  11. 11. Lesson objectivesYou are now able to:1. define photosynthesis.2. classify the various factors ofphotosynthesis into either raw materialsor conditions required forphotosynthesis.3. state the word and chemical equation forphotosynthesis.
  12. 12. Video: The photosynthesissonghttp://www.youtube.com/watch?v=C1_uez5WX1o
  13. 13. Video to recap the lastlessonhttp://www.youtube.com/watch?v=eJQxHoqIPIM&fTake note: The chemicalequation is not balanced!
  14. 14. Lesson objectivesAt the end of the lesson, you will be ableto:1. describe the steps involved in testing aleaf for starch to see if photosynthesishas taken place.2. state the reason behind each step intesting a leaf for starch.
  15. 15. Why do we test the leaf forstarch instead of glucose?Starch is a good storage molecule as itis– insoluble in water– used only when needed.
  16. 16. How do we tell if Photosynthesishas taken place?• Test for StarchGlucose + OxygenLight energychlorophyll(stored asstarch)Carbon dioxide + WaterUse Iodine test
  17. 17. To Test for Starch in a Leaf1.Place leaf in boiling water.To stop chemical reactions in the leaf so thatenzymes will stop converting starch to glucose.2.Place leaf in hot alcohol /ethanol.To remove the green chlorophyll(decolourisation) so the final results can beclearly seen.           Bunsen burner turned offAlcohol turned green
  18. 18. 3. Dip leaf into warm waterTo remove the alcohol on the leaf/to soften the leaf4. Spread leaf evenly on white tile.Cover leaf with iodine solutionto test for the presence of starch.5. Leaf turns blue-black if starch ispresent.Leaf turns light brown, starch isabsent
  19. 19. Iodine test videohttp://www.youtube.com/watch?v=VeU7ULL9Usw
  20. 20. Lesson objectivesYou are now able to:1. describe the steps involved in testing a leaf for starch to see if photosynthesis has taken place.2.  state  the  reason  behind  each  step  in testing a leaf for starch.
  21. 21. Lesson objectivesAt the end of the lesson, you will be able to:1. state the factors affecting the rate of photosynthesis and interpret related graphs.2. describe the steps involved in testing how various factors can affect the rate of photosynthesis
  22. 22. ChlorophyllLightIntensity CarbonDioxideConcentrationTemperature
  23. 23. Factors affecting rate ofphotosynthesis
  24. 24. Experiments used to show how certain factors can affect the rate of photosynthesis.
  25. 25. As future scientists, these are the things to look out for before we carry out an experiment….1. What is the result we are looking for?2. What factor are we changing in the experiment?
  26. 26. • Keep in a darkplace for 24-48hours (1 to 2days)- any stored starchwill be converted tosugars which aretransported to otherparts of the plantHow to destarch a plant?
  27. 27. • To ensure that starch isabsent from the leaves atthe beginning of anexperiment, so that if anystarch is formed, thenphotosynthesis must havetaken placeWhy destarch a plant?
  28. 28. As future scientists, these are the things to look out for before we carry out an experiment….1. What is the result we are looking for?2. What factor are we changing in the experiment?
  29. 29. Lesson objectivesAt the end of the lesson, you will be able to:1. describe the steps involved in testing how various factors can affect the rate of photosynthesis.2. define respiration.3. write the word and chemical equation for respiration.
  30. 30. Lesson objectivesAt the end of the lesson, you will be able to:1. describe the steps involved in testing how various factors can affect the rate of photosynthesis.2. define respiration.3. write the word and chemical equation for respiration.
  31. 31. • To ensure that starch isabsent from the leaves atthe beginning of anexperiment, so that if anystarch is formed, thenphotosynthesis must havetaken placeWhy destarch a plant?
  32. 32. • Keep in a darkplace for 24-48hours (1 to 2days)- any stored starchwill be converted tosugars which aretransported to otherparts of the plantHow to destarch a plant?
  33. 33. ChlorophyllLightIntensity CarbonDioxideConcentrationTemperature
  34. 34. To find out whether sunlight isnecessary for photosynthesisWithsunlightWithoutsunlight
  35. 35. To find out whether carbon dioxide isnecessary for photosynthesisSoda lime toabsorb CO2Sodium hydroxideto absorb CO2Without carbondioxideWith carbondioxide
  36. 36. White(withoutchlorophyll)Green(withchlorophyll)brownBlue-blackTo find out whether chlorophyll is essential forphotosynthesisVariegated leaf
  37. 37. o find out what gas is given off duringphotosynthesisOxygen gasreleased from thecut end of thestem
  38. 38. To find out what gas is given off duringphotosynthesisToprovideCO2
  39. 39. Why is Photosynthesisimportant?Provides food and energyfor animals (primaryproducers).Produces oxygen andremoves carbon dioxidefrom the air.
  40. 40. RespirationProcess by which food molecules arebroken down to release energy.• Energy is used for:– muscle movement,– maintain constant body temperature,– for growth etc.
  41. 41. Respiration• Oxygen taken in, Carbon dioxidegiven out• Takes place all the time in livingorganisms, be it in plants or inanimals.
  42. 42. Respiration: Word equationGlucose + Oxygen  Carbon dioxide + Water + EnergyAerobicrespiration•Oxygen isrequired
  43. 43. Lesson objectivesYou are now able to:1. describe the steps involved in testing howvarious factors can affect the rate ofphotosynthesis.2. define respiration.3. write the word and chemical equation forrespiration.
  44. 44. Lesson objectivesAt the end of the lesson, you will be ableto:1. interpret graphs relating to photosynthesisand respiration.2. compare and contrast betweenphotosynthesis and respiration.
  45. 45. blue blackblue-blackRawmaterialsConditions
  46. 46. Net uptake/release of gasesRate of photosynthesis > rate of respirationNet uptake of CO2 > Net release of CO2Net release of oxygen > Net uptake of oxygenRate of respiration > rate of photosynthesisNet release of CO2 > Net uptake of CO2Net uptake of oxygen > Net release of oxygen
  47. 47. Photosynthesis/ RespirationNetreleaseofoxygenNetuptakeofoxygen6 am midday 6 pm midnightXTime of dayrate of photosynthesis=rate of respirationXYrate of photosynthesis>rate of respirationZrate of respiration > rate of photosynthesis20-15-10-5 -05 -10-15-20-
  48. 48. Q: Why should you not have any greenplants in your bedroom at night?At night, green plants do notphotosynthesise due to the absence oflight. Respiration takes place and thegreen plants will compete with you foroxygen.
  49. 49. Lesson objectivesYou are now able to:1. interpret graphs relating to photosynthesisand respiration.2. compare and contrast betweenphotosynthesis and respiration.
  50. 50. DIFFERENCESBETWEEN• PHOTOSYNTHESIS • RESPIRATIONCan you differentiatebetween photosynthesis &respiration?Write on a foolscap paper!
  51. 51. Thinking time!Why do some people say that plants formthe ‘lungs’ of the earth?
  52. 52. Producers
  53. 53. Think of plants makingtheir own food like…your parents makingfood for you
  54. 54. Parents preparingfood for youPlants making theirown foodProcess:Ingredients used:CookingRiceVegetablesEggProcess:?Ingredients used:?
  55. 55. E-revision questions(To be completed)
  56. 56. Think about it…Instruction: Please revise through the chapter using thepowerpoint slides provided and try this on your own beforereferring to the answer scheme which will be uploadedtomorrow. Google is a good tool to use to research for theanswers!•1a. Do you think that red leaves contains chlorophyll? Ifyes, how do you explain the red colour of the leaf? If no,why not?•1b. Hence, do you think that the red leaf canphotosynthesise? Why or why not?
  57. 57. To fill inInstruction: Please revise through the chapter using thepowerpoint slides provided and try this on your own beforereferring to the answer scheme which will be uploadedtomorrow.Similarities and differences between Photosynthesis and RespirationPhotosynthesis RespirationSimilaritiesDifferences
  58. 58. To complete (1)Instruction: Please revise through the chapter using thepowerpoint slides provided and try the following question(this question comprises of the next 3 slides) beforereferring to the answer scheme which will be uploadedtomorrow.Concept: Factors affecting photosynthesis
  59. 59. To complete (2)Concept: Factors affecting photosynthesis
  60. 60. To complete (3)Concept: Factors affecting photosynthesis

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