1. Photosynthesis 8-1 Energy and Life

2. Energy Who needs energy? Who needs energy? Why? Why? Where do plants get this energy? Where do plants get this energy? What about animals? What about animals?

3. Autotrophs/Heterotrophs Auto (self) Auto (self) Hetero (other) Hetero (other) Troph (nourishing) Troph (nourishing) Organisms, such as plants, which make their own food, are called autotrophs. Organisms, such as plants, which make their own food, are called autotrophs. Organisms, such as animals, that must obtain energy from the foods they consume are heterotrophs. Organisms, such as animals, that must obtain energy from the foods they consume are heterotrophs.

4. ATP: energy for life  Energy is required by every process which occurs in a cell/organism. It comes in many forms (heat/light/electrical/etc.)  Chemical energy is the form preferred by life because it can be stored. Is provided to organisms in the form of chemical bonds in food molecules (ex. carbohydrates, fats)  This takes time to break down during digestion. It’s slow to access. ATP is a much more readily available chemical form of energy and it can be made using the energy obtained from eating.

5. Chemical Energy and ATP ATP consists of: ATP consists of: adenine adenine ribose (a 5-carbon sugar) ribose (a 5-carbon sugar) 3 phosphate groups 3 phosphate groups Adenine ATP Ribose 3 Phosphate groups

6. Chemical Energy and ATP Storing Energy Storing Energy ADP has two phosphate groups instead of three. ADP has two phosphate groups instead of three. A cell can store small amounts of energy by adding a phosphate group to ADP. A cell can store small amounts of energy by adding a phosphate group to ADP. ADP ATP Energy Partially charged battery Fully charged battery + Adenosine Diphosphate (ADP) + Phosphate Adenosine Triphosphate (ATP)

7. Chemical Energy and ATP Releasing Energy Releasing Energy Energy stored in ATP is released by breaking the chemical bond between the second and third phosphates. Energy stored in ATP is released by breaking the chemical bond between the second and third phosphates. P ADP 2 Phosphate groups

8. ADP P + = mitochondrion = protein molecule (ex. transport protein) (phosphorylated molecule -- energized; can now do cellular work by passing along energy received from binding to P from ATP) P Inorganic Phosphate from cytoplasm

9. Uses of ATP Active Transport Active Transport Protein synthesis Protein synthesis Muscle contraction Muscle contraction ATP is not stored in large amounts because cells can regenerate ATP from ADP as needed by using the energy from the food we eat (glucose). ATP is not stored in large amounts because cells can regenerate ATP from ADP as needed by using the energy from the food we eat (glucose).

10. 8-1  Organisms that make their own food are called a.autotrophs. b.heterotrophs. c.decomposers. d.consumers.

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12. What’s going on? How does the amount of gas in each test tube differ? How does the amount of gas in each test tube differ? What do you think the gas is? What do you think the gas is? Based on the results of this inquiry, what factor is necessary for photo- synthesis to occur? Based on the results of this inquiry, what factor is necessary for photo- synthesis to occur?

13. Studies on photosynthesis began in the 1600’s! Priestly, Ingenhousz, Van Helmont: Look ‘em up! p. 204-06 Priestly, Ingenhousz, Van Helmont: Look ‘em up! p. 204-06 In general, they discovered: In general, they discovered: in the using the energy of light, plants transform carbon dioxide and water into high energy carbohydrates, and they also release oxygen. in the using the energy of light, plants transform carbon dioxide and water into high energy carbohydrates, and they also release oxygen.

14. Overall reaction equation: Overall reaction equation: LIGHT!+ CO 2 + H 2 O ----> C 6 H 12 O 6 + O 2 [Raw materials] [Products] CO 2 comes from the atmosphere CO 2 comes from the atmosphere H 2 O comes from the ground water H 2 O comes from the ground water Light (comes from within… just kidding, it comes from the sun) Light (comes from within… just kidding, it comes from the sun) Photosynthesis

15. Properties of Light Light can be: Reflected Transmitted Absorbed Which process is important for photosynthesis?

16. Light Light is a form of energy, so any compound that absorbs light also absorbs energy from that light. Light is a form of energy, so any compound that absorbs light also absorbs energy from that light. Only the visible spectrum can be absorbed in photosynthesis. Only the visible spectrum can be absorbed in photosynthesis.

17. Each light color has its own level of energy Wavelength 1 second = LEAST energy 1 second = MEDIUM amount of energy 1 second = MOST energy What kind of energy would yellow light contain? Ultraviolet?

18. Chlorophyll Pigments like Chlorophyll absorb light energy. Pigments like Chlorophyll absorb light energy. Two main types: Chlorophyll A, Chlorophyll B Two main types: Chlorophyll A, Chlorophyll B much of the energy is transferred directly to electrons in the chlorophyll molecule, raising the energy levels of these electrons. much of the energy is transferred directly to electrons in the chlorophyll molecule, raising the energy levels of these electrons. These high-energy electrons are what make photosynthesis work. These high-energy electrons are what make photosynthesis work.

19. Chlorophyll molecules a, b (c, d found in algae) Ring portion absorbs light rays Accessory pigments (these pigment molecules absorb colors not absorbed by chlorophyll): Carotenoids (yellow-orange) Xanthophyll (yellow) Fucoxanthin (brown) Phycobilins (green, violet, and blue )

20. What portion of spectrum is absorbed and used in photosynthesis? White line = colors mostly absorbed by the different chlorophylls (Left axis scale) Black line = colors most used after being absorbed. (Right axis scale)

21. Inside a Chloroplast Inside a Chloroplast Inside a Chloroplast In plants, photosynthesis takes place inside chloroplasts. In plants, photosynthesis takes place inside chloroplasts. Plant Plant cells Chloroplast

22. Inside a Chloroplast Chloroplasts contain thylakoids—saclike photosynthetic membranes. Chloroplasts contain thylakoids—saclike photosynthetic membranes. Chloroplast Single thylakoid

23. Inside a Chloroplast Thylakoids are arranged in stacks known as grana. A singular stack is called a granum. Thylakoids are arranged in stacks known as grana. A singular stack is called a granum. Granum Chloroplast

24. Inside a Chloroplast Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters called photosystems, which are the light-collecting units of the chloroplast. Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters called photosystems, which are the light-collecting units of the chloroplast. Chloroplast Photosystems

25. Arrangement of chlorophylls and accessory pigments –– light-harvesting antennae (clusters of pigment molecules) All pigment molecules can absorb different light energies, but only one molecule can send an excited electron to the primary electron acceptor -- that one must be a chlorophyll molecule. Thylakoids (flat sacs stacked into a granum) Photosystem (collection of pigment molecules)

26. Details of a thylakoid Stroma

27. Who goes where? CO 2 + H 2 O +light -> C 6 H 12 O 6 + O 2 CO 2 + H 2 O +light -> C 6 H 12 O 6 + O 2 How are the reactants rearranged to form sugar and oxygen? See the experiment below: How are the reactants rearranged to form sugar and oxygen? See the experiment below: Make oxygen of H 2 O radioactive with isotope 18 O so that it can be traced through the photosynthesis reactions. Make oxygen of H 2 O radioactive with isotope 18 O so that it can be traced through the photosynthesis reactions. CO 2 + H 2 18 O ------> C 6 H 12 O 6 + 18 O 2 CO 2 + H 2 18 O ------> C 6 H 12 O 6 + 18 O 2 Meaning? Light energy is used to split H 2 O during the reactions. Meaning? Light energy is used to split H 2 O during the reactions. So H’s get stuck to CO 2 to make sugar! How? So H’s get stuck to CO 2 to make sugar! How?

28. Light-Dependent Reactions uses water, ADP, and NADP +. uses water, ADP, and NADP +. produces oxygen, ATP, and NADPH. produces oxygen, ATP, and NADPH. ATP and NADPH (low energy compounds) provide the energy to build higher energy-containing sugars that are more stable and can be stored. ATP and NADPH (low energy compounds) provide the energy to build higher energy-containing sugars that are more stable and can be stored.

29. Light-dependent Reactions Begins with high-energy (excited) electrons. 1.The energy is given to enzymes to Split 2H 2 O -----> 4H + + O 2 (escapes to atmosphere) Four electrons, four H + ions and two oxygen atom are released. The electrons are used to help make NADPH. H + is used to make ATP (see following slides) NADP.+ --------> NADPH 2. ADP + P i -----------> ATP These are used in the light-independent reactions

30. The Photosynthesis Equation O2O2 CO 2 + H 2 O Sugar ADP NADP + Light-Dependent Reactions (thylakoids) H2OH2O ATP NADPH Calvin Cycle (stroma) Light energy

31. Light-Dependent Reactions

32. Photosystem II Light-Dependent Reactions Photosynthesis begins when pigments in photosystem II absorb light, increasing the energy level of their electrons. Photosynthesis begins when pigments in photosystem II absorb light, increasing the energy level of their electrons.

33. Light-Dependent Reactions Photosystem II 2H 2 O The energy is given to enzymes on the thylakoid membrane which break water molecules into: The energy is given to enzymes on the thylakoid membrane which break water molecules into: H+ ions, O2 molecules, and free electrons which get passed into a chain of proteins within the membrane of the thylakoid (electron transport chain). H+ ions, O2 molecules, and free electrons which get passed into a chain of proteins within the membrane of the thylakoid (electron transport chain). Electron carriers High-energy electron + O 2

34. Light-Dependent Reactions Photosystem II 2H 2 O + O 2 The energized electrons from water replace the high-energy electrons that chlorophyll lost to the electron transport chain. High-energy electron

35. Light-Dependent Reactions Photosystem II 2H 2 O As plants remove electrons from water, oxygen is left behind and is released into the air. + O 2 High-energy electron

36. Light-Dependent Reactions Photosystem II 2H 2 O The hydrogen ions left behind when water is broken apart are released inside the thylakoid membrane. + O 2 High-energy electron

37. Light-Dependent Reactions Photosystem II 2H 2 O Energy from the electrons is used to transport H + ions from the stroma into the inner thylakoid space. + O 2

38. Light-Dependent Reactions Photosystem II 2H 2 O High-energy electrons move through the electron transport chain from photosystem II to photosystem I. + O 2 Photosystem I

39. Light-Dependent Reactions 2H 2 O Pigments in photosystem I use energy from light to re-energize the electrons. + O 2 Photosystem I

40. Light-Dependent Reactions 2H 2 O NADP + then picks up these high-energy electrons, along with H + ions, and becomes NADPH. + O 2 2 NADP + 2 NADPH 2

41. Light-Dependent Reactions 2H 2 O As electrons are passed from chlorophyll to NADP +, more H + ions are pumped across the membrane. + O 2 2 NADP + 2 NADPH 2

42. Light-Dependent Reactions 2H 2 O Soon, the inside of the membrane fills up with positively charged hydrogen ions, which makes the outside of the membrane negatively charged. + O 2 2 NADP + 2 NADPH 2

43. Light-Dependent Reactions 2H 2 O The difference in charges across the membrane provides the energy to make ATP + O 2 2 NADP + 2 NADPH 2

44. Light-Dependent Reactions 2H 2 O H + ions cannot cross the membrane directly. + O 2 ATP synthase 2 NADP + 2 NADPH 2

45. Light-Dependent Reactions 2H 2 O The cell membrane contains a protein called ATP synthase that allows H + ions to pass through it + O 2 ATP synthase 2 NADP + 2 NADPH 2

46. Light-Dependent Reactions 2H 2 O As H + ions pass through ATP synthase, the protein rotates. + O 2 ATP synthase 2 NADP + 2 NADPH 2

47. Light-Dependent Reactions 2H 2 O As it rotates, ATP synthase binds ADP and a phosphate group together to produce ATP. + O 2 2 NADP + 2 NADPH 2 ATP synthase ADP

48. Light-Dependent Reactions 2H 2 O Because of this system, light-dependent electron transport produces not only high-energy electrons but ATP as well. + O 2 ATP synthase ADP 2 NADP + 2 NADPH 2

49. e–e– H 2 O ----> H + + e – + O 2 Overview of Light reactions (in thylakoid membranes) ADP + P i ATP e–e– NADP + H + NADPH Calvin Cycle Photosystem II Photosystem I Electron transport chain e-e- v e-e- v e-e- v e-e- v Stroma Light-independent- in stroma (thick liquid between thylakoids) H+H+ NOW, YOU DRAW IT!

50. Electron Carriers The NADPH carries high-energy electrons to chemical reactions elsewhere in the cell. The NADPH carries high-energy electrons to chemical reactions elsewhere in the cell. These high-energy electrons are used to help build a variety of molecules the cell needs, including carbohydrates like glucose. These high-energy electrons are used to help build a variety of molecules the cell needs, including carbohydrates like glucose.

51. The Calvin Cycle Six carbon dioxide molecules enter the cycle from the atmosphere and combine with six 5-carbon molecules. Six carbon dioxide molecules enter the cycle from the atmosphere and combine with six 5-carbon molecules. CO 2 Enters the Cycle

52. The Calvin Cycle The result is twelve 3-carbon molecules, which are then converted into higher-energy forms. The result is twelve 3-carbon molecules, which are then converted into higher-energy forms.

53. The Calvin Cycle The energy for this conversion comes from ATP and high-energy electrons from NADPH. The energy for this conversion comes from ATP and high-energy electrons from NADPH. 12 NADPH 12 12 ADP 12 NADP + Energy Input

54. The Calvin Cycle Two of twelve 3-carbon molecules are removed from the cycle. Two of twelve 3-carbon molecules are removed from the cycle. Energy Input 12 NADPH 12 12 ADP 12 NADP +

55. The Calvin Cycle The molecules are used to produce sugars, lipids, amino acids and other compounds. The molecules are used to produce sugars, lipids, amino acids and other compounds. 12 NADPH 12 12 ADP 12 NADP + 6-Carbon sugar produced Sugars and other compounds

56. The Calvin Cycle The 10 remaining 3-carbon molecules are converted back into six 5-carbon molecules, which are used to begin the next cycle. The 10 remaining 3-carbon molecules are converted back into six 5-carbon molecules, which are used to begin the next cycle. 12 NADPH 12 12 ADP 12 NADP + 5-Carbon Molecules Regenerated Sugars and other compounds 6 6 ADP

57. and all other chemicals a plant needs Thylakoid membranes Stroma Carbon fixation reactions

58. Inside a Chloroplast Chloroplast Light H2OH2O O2O2 CO 2 Sugars NADP + ADP + P Calvin Cycle Light- dependent reactions Calvin cycle

59. Factors Affecting Photosynthesis Many factors affect the rate of photosynthesis, including: Many factors affect the rate of photosynthesis, including: Water Water Temperature Temperature Intensity of light Intensity of light

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