2. PHOTOSYNTHESIS Review Your Understanding AP Biology Begin Presentation Begin Presentation

3. Overview This interactive presentation will review the major concepts involved in photosynthesis allowing you to focus on areas that are least clear. At the end of the presentation there will be a quiz to test your understanding. Click the following image now (and at anytime) to go to the main menu.

4. Main Menu What is Photosynthesis Photosynthetic Pigments Site of Photosynthesis Photosystems – (Capture) Light-Dependent Reactions – (Convert) Light-Independent Reactions – (Store) AP Biology Lab 4 Quiz

5. Photosynthesis Autotrophic organisms are able to manufacture their own organic food molecules from inorganic molecules. Most autotrophs use sunlight as their energy source but some use inorganic chemical bond energy in a process call chemosynthesis. Autotrophs which contain the green pigment chlorophyll (located in their chloroplast) are able to convert solar energy into stored chemical bond energy in a process called photosynthesis. NEXT  NEXT 

6. The following reaction (in the presence of light) summarizes the chemical process of photosynthesis. –Carbon dioxide + water  glucose + oxygen + water –6CO 2 + 12H 2 O  C 6 H 12 O 6 + 6O 2 + 6H 2 O This process can be broken down into 3 stages –The capture of light energyThe capture of light energy –The conversion of light energy into chemical energyThe conversion of light energy into chemical energy –The storage of chemical energy in sugar (carbon fixation)The storage of chemical energy in sugar (carbon fixation) The first 2 stages are referred to as the light-dependent reactions while the last stage refers to the light– independent reactions. Photosynthesis  BACK  BACK NEXT  NEXT 

7. Overview  BACK  BACK

8. Photosynthetic Pigments The sun radiates light energy in individual packets called photons. The energy of a photon corresponds to its wavelength. »Wavelength of Visible Light The first step in photosynthesis is the capture of photons by pigments in the chloroplast. NEXT  NEXT 

9. A pigment absorbs all colors that it does not reflect. The chloroplast contains several types of pigment molecules that absorb different wavelengths of light. Chlorophyll is the key light capturing pigment (containing > 120 atoms) found in the thylakoid membrane of the chloroplast. It strongly absorbs violet, blue, and red light but reflects green, and therefore appears green. See graphSee graph Photosynthetic Pigments NEXT  NEXT   BACK  BACK

10. Figure 1. Different types of pigments selectively absorb certain colors; the height of each line represents the ability of each pigment to absorb light of each color. Photosynthesis is driven to some extent by all of the colors of light, owing to the absorption of light by several thylakoid pigments.  BACK  BACK

11. Thylakoids also contain other molecules called antenna/accessory pigments, that capture light energy and transfer it to chlorophyll, thus expanding the spectrum of light that can be used in photosynthesis. Carotenoids and xanthophylls  absorb blue and green light and appear yellow, orange or red. Phycocyanins  absorb green and yellow light and appear blue or purple. –See graphSee graph Photosynthetic Pigments  BACK  BACK

12. Where Photosynthesis Happens The main photosynthetic structure of a plant is the leave. - Mesophyll cells contain the chloroplasts used in photosynthesis. - Necessary CO 2 and O 2 exchange occurs via the stoma. NEXT  NEXT  Cross section of a leaf

13. Chloroplast Here we see a single mesophyll cell and some of its major features including a nucleus, vacuole, and the green chloroplast NEXT  NEXT   BACK  BACK

14. Structure of a Chloroplast Refer to diagram on preceding page Refer to diagram on preceding page The chloroplast is surrounded by a double membrane enclosing a semifluid medium know as stroma. Embedded in the stroma are disk-shaped, interconnected membranous sacs called thylakoids. A stack of thylakoids is referred to as granum (grana, plural).  BACK  BACK

15. Photosystems In the thylakoid membrane, chlorophyll, antenna pigments, and electron-carrier molecules form highly organized assemblies called photosystems which capture light. Each thylakoid contains thousands of copies of two different kinds of photosystems. Each is made up of 2 parts, a light harvesting complex and an electron transport system. NEXT  NEXT 

16. These light-harvesting complexes consist of a reaction center containing chlorophyll plus antenna pigments. The reaction center is located next to the electron transport system – a series of electron carriers in the thylakoid membrane. The 2 photosystems are referred to as PS 1 and PS II or P700 and P680, respectively. Photosystems  BACK  BACK NEXT  NEXT 

17. PS I (P700) absorbs light, on the average in the 700 nm range. PS II(P680) absorbs light, on the average in the 680 nm range. PS II activates before PS I Photosystems  BACK  BACK NEXT  NEXT 

18. Photosystem II Lets take a closer look In the following video you will see: –The processes that take place in the PS II complex –How chlorophyll pigments become excited by light energy –How an electron is transferred to the electron transport chain –How oxygen is generated form water VIDEO  BACK  BACK

19. Light-Dependent Reaction Occurs in clusters of molecules called photosystems (in the thylakoid membrane) Energy from the sun is converted into chemical energy in the form of adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADPH). This energy is needed to later fuel the light independent (Calvin Cycle) in the stroma. NEXT  NEXT 

20. Light-Dependent Reaction The reaction begins when light is absorbed by chlorophyll pigments in PS II located within the thylakoid membrane. An excited electron will then pass through the electron transport chain until it reaches PS I Through this process energy (ATP and NADPH) is made.  BACK  BACK NEXT  NEXT 

21. Use the following animation to study the steeps of the light-dependent reaction. Animation – click the play button (►) at the bottom right to begin. Place your mouse over each object to reveal the name of that object.Animation When you have finished close the webpage and return to this presentation. Click ‘next’ to see the steeps in the light-dependent reaction. Light-Dependent Reaction NEXT  NEXT   BACK  BACK

22. 1.Light is harvested in photosystem II 2.This energy ejects electrons out of the reaction center 3.Electrons pass to the adjacent electron transport system 4.The transport system passes the electrons along, some of their energy is used to pump hydrogen ions into the thylakoid interior. A hydrogen gradient results and drives ATP synthesis 5.Light strikes photosystem I 6.PS I emits electrons 7.These electrons are captures by PS I electron transport system. Electrons lost from PS I reaction center are replaced by those coming from the transport system of PS II. 8.High energy electrons from PS I are captured by NADP+, which becomes NADPH 9.The electrons lost from the reaction center of PS II are replaced by electrons obtained from the splitting of water (photolysis). This liberates oxygen (O 2 ) Light-Dependent Reaction Process  **See diagram** **See diagram** NEXT  NEXT   BACK  BACK

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24. Lets go to the video! To see a video of the light reaction in progress click the following link –VIDEO VIDEO As the page loads, study the diagram again –**See diagram****See diagram**  BACK  BACK NEXT  NEXT 

25. ATP is produced: The flow of electrons through electron transport chains is coupled with the phosphorylation of ADP to ATP via chemiosmosis phosphorylation –ATP is needed to fuel the light independent reactions (Calvin Cycle) Oxygen is produced: Water is split apart via Photolysis to provide electrons for photosystem II and protons to reduce NADP in photosystem I. NADPH is produced: NADP+ carries H 2 to the light-independent reactions (Calvin Cycle). Light-Dependent Reaction Summary NEXT  NEXT   BACK  BACK

26. The main process occurring during the light- dependent reaction. Light energy (‘photo’) is used to ‘phosphorylate’ ADP, forming ATP. Process begins at PS II and continues in PS I Electrons supplied by photolysis enter two electron transport chains and ATP and NADPH are formed Chemiosmosis powers the production of ATP Photophosphorylation  BACK  BACK

27. Light-Independent Reactions Storing chemical energy in sugar molecules, occurs in the stoma. ATP and NADPH (synthesized during the light-dependent reactions) are dissolve in the stoma, providing the energy to power the synthesis of glucose from CO 2 and H 2 0. Reaction occurs independently of light as long as ATP and NADPH are available. NEXT  NEXT 

28. Light-Independent Reactions CO 2 capture occurs in a set of reactions know as the Calvin cycle or C 3 cycle. The Calvin/C 3 cycle requires; –CO 2 (normally from the air) –A CO 2 capturing sugar, ribulose bisphosphate (RuBP) –Enzymes to catalyze all the reactions –Energy in the form of ATP and NADPH (from the light- dependent reactions)  BACK  BACK NEXT  NEXT 

29. Use the following animation to study the steeps of the Calvin Cycle. Animation – click the 5 carbon molecule RuBP to begin. Use the flow chart on the right to proceed steep by steep through the cycle.Animation When you have finished close the webpage and return to this presentation. Click ‘next’ to see the parts of the Calvin cycle. Calvin Cycle NEXT  NEXT   BACK  BACK

30. Calvin Cycle CO 2 (from the atmosphere) is chemically reduced by hydrogen ions (produced in the light-dependent reactions) to produce carbohydrates CO 2 + H  CH 2 O (unbalanced) The Calvin/C 3 cycle is best understood in three parts (be sure to look at each before continuing) 1.Carbon fixationCarbon fixation 2.Synthesis of phosphoglyceraldehyde (PGAL)Synthesis of phosphoglyceraldehyde (PGAL) –A 3 carbon sugar 3.The regeneration of ribulose biphosphate (RuBP)The regeneration of ribulose biphosphate (RuBP)  BACK  BACK NEXT  NEXT 

31. Carbon Fixation Section #1 of diagram Section #1 of diagram The Calvin cycle begins and ends with a 5- carbon sugar, RuBP. RuBP combines with CO 2 from the atmosphere to form an extreamly unstabe 6-carbon compound. This spontaneously reacts with H 2 O to form two 3-carbon molecules of phosphoglyceric acid PGA (hence C 3 cycle)  BACK  BACK

32. Synthesis of PGAL Section #2 of diagram Section #2 of diagram A series of enzyme-catalyzed reactions occur. Energy donated by ATP and NADPH, generated in the light reactions, is used to convert PGA to phosphoglyceraldehyde (PGAL).  BACK  BACK

33. Regeneration of RuBP Section #3 of diagram Section #3 of diagram A complex series of reactions requiring ATP energy occurs. Ten molecules of PGAL (10 x 3-carbon) can regenerate 6 molecules of RuBP (6 x 5-carbon). These six RuBP molecules are used to start the cycle again.  BACK  BACK

34. Click to go back to Step #1 Click to go back to Step #1 Click to go back to Step #2 Click to go back to Step #2 Click to go back to Step #3 Click to go back to Step #3

35. Calvin Cycle End Results The Calvin Cycle starts with 6 molecules of RuBP, adds CO 2 to each, and ends with 6 molecules of RuBP again. The fixed carbon (from atmospheric CO 2 ) has been transformed and two molecules of phosphoglyceraldehyde (PGAL) are left over. These two PGAL molecules (3-carbon each) combine to form one glucose (6-carbon) Glucose can later be broken down (respiration) or linked together to form starch (storage) or cellulose (cell walls), or modified into other cellular contents.  BACK  BACK

36. Lab Activity Go to the following link to review Plant Pigments and Photosynthesis. Be sure to look at part II of the lab as we do not have the materials at the school to do this part of the lab. Click me

37. Quiz The following is a short quiz covering some of the important ideas of photosynthesis. If you select a wrong answer, you will be given an explanation of why it is incorrect. You can not move to the next question until you choose the correct answer NEXT  NEXT 

38. QUESTION #1 Which of the following are products of photosynthesis? A) Carbon dioxide and water B) Carbon dioxide and glucose C) Glucose and oxygen D) Oxygen and caclcium

39. Q #1  A Incorrect A is incorrect because carbon dioxide and water are the products of aerobic respiration Return to Question #1 Return to Question #1

40. Q #1  B Incorrect B is incorrect because only one of these is a product of photosynthesis! Return to Question #1 Return to Question #1

41. Q #1  C CORRECT C is correct because the products of photosynthesis are oxygen and glucose. –Carbon dioxide + water  glucose + oxygen + water 6CO 2 + 12H 2 O  C 6 H 12 O 6 + 6O 2 + 6H 2 O NEXT QUESTION NEXT QUESTION

42. Q #1  D Incorrect D is incorrect because only one of these is a product of photosynthesis! Return to Question #1 Return to Question #1

43. QUESTION #2 What is the name of the pigment used to trap light energy during the process of photosynthesis? A) PGAL B) ATP C) Chlorophyll D) Stoma

44. Q #2  A Incorrect A is not correct because PAGL is the first organic compound produced during photosynthesis Return to Question #2 Return to Question #2

45. Q #2  B Incorrect B is not correct because ATP is a chemical found in living organisms used to store and release energy. Return to Question #2 Return to Question #2

46. Q #2  C CORRECT C is the correct answer because the chemical used to trap light energy during photosynthesis is chlorophyll. NEXT QUESTION NEXT QUESTION

47. Q #2  D Incorrect D is incorrect because the stoma is the region inside the chloroplast of the cell. Return to Question #2 Return to Question #2

48. QUESTION #3 A water molecule is split into hydrogen and hydroxide ions during the process of what? A) Chemosynthesis B) Hydrolysis C) Photolysis D) Carbon fixation

49. Q #3  A Incorrect A is not correct because chemosynthesis is the manufacturing of organic molecules by using chemical energy located in inorganic molecules. Return to Question #3 Return to Question #3

50. Q #3  B Incorrect B is not correct because hydrolysis is the splitting of two molecules with the addition of water. Return to Question #3 Return to Question #3

51. Q #3  C CORRECT C is correct because photolysis is the splitting of water molecules. NEXT QUESTION NEXT QUESTION

52. Q #3  D Incorrect D is not correct because carbon fixation is the chemical process where atmospheric carbon dioxide is captured by plants. Return to Question #3 Return to Question #3

53. QUESTION #4 What energy conversion occurs during the process of photosynthesis? A) Light energy to nuclear energy B) Chemical bond energy to light energy C) Light energy to chemical bond energy D) Mechanical energy to radiant energy

54. Q #4  A Incorrect A is not correct because this type of energy conservation does not occur in photosynthesis. Return to Question #4 Return to Question #4

55. Q #4  B Incorrect B is not correct because this type of energy conservation does not occur in photosynthesis. Return to Question #4 Return to Question #4

56. Q #4  C Correct C is the correct answer because the energy conservation that occurs during photosynthesis is light energy to chemical bond energy. NEXT QUESTION NEXT QUESTION

57. Q #4  D Incorrect B is not correct because this type of energy conservation does not occur in photosynthesis. Return to Question #4 Return to Question #4

58. QUESTION #5 The coenzyme that carries hydrogen atoms from the light reaction to the dark reaction is? A) NADP B) Chlorophyll C) ATP D) RNA

59. Q #5  A CORRECT A is the correct answer because NADP is the coenzyme that carries hydrogen atoms from the light reaction to the dark reaction. End of Presentation End of Presentation

60. Q #5  B Incorrect B is not the correct answer because chlorophyll is the chemical in photosynthetic plants used to trap light energy for food production. Return to Question #5 Return to Question #5

61. Q #5  C Incorrect C is not the correct answer because ATP is a chemical found in living organisms used to store and release energy. Return to Question #5 Return to Question #5

62. Q #5  D Incorrect D is not the correct answer because RNA is a nucleic acid that aids in protein synthesis. Return to Question #5 Return to Question #5

63. THE END Mr. Young AP Biology 2007/2008