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T HE R EACTIONS OF P HOTOSYNTHESIS Photosynthesis songPhotosynthesis song ~ Enjoy!

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Presentation on theme: "T HE R EACTIONS OF P HOTOSYNTHESIS Photosynthesis songPhotosynthesis song ~ Enjoy!"— Presentation transcript:

1 T HE R EACTIONS OF P HOTOSYNTHESIS Photosynthesis songPhotosynthesis song ~ Enjoy!

2 I NSIDE A C HLOROPLAST Inside a Chloroplast In plants, photosynthesis takes place inside chloroplasts. Copyright Pearson Prentice Hall Plant Plant cells Chloroplast

3 I NSIDE A C HLOROPLAST Chloroplasts contain thylakoids —saclike photosynthetic membranes. Copyright Pearson Prentice Hall Chloroplast Single thylakoid

4 I NSIDE A C HLOROPLAST Thylakoids are arranged in stacks known as grana. A singular stack is called a granum. Copyright Pearson Prentice Hall Granum Chloroplast

5 I NSIDE A C HLOROPLAST Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters called photosystems, which are the light-collecting units of the chloroplast. Copyright Pearson Prentice Hall Chloroplast Photosystems

6 I NSIDE A C HLOROPLAST The light-dependent reactions take place within the thylakoid membranes. The Calvin cycle (AKA: light-independent reaction) takes place in the stroma, which is the region outside the thylakoid membranes. The two sets of photosynthetic reactions work together. The light-dependent reactions trap sunlight energy in chemical form. The light-independent reactions use that chemical energy to produce stable, high-energy sugars from carbon dioxide and water.

7 I NSIDE A C HLOROPLAST Copyright Pearson Prentice Hall Chloroplast Light H2OH2O O2O2 CO 2 Sugars NADP + ADP + P Calvin Cycle Light- dependent reactions Calvin cycle

8 E LECTRON C ARRIERS When electrons in chlorophyll absorb sunlight, the electrons gain a great deal of energy. Cells use electron carriers to transport these high- energy electrons from chlorophyll to other molecules. One electron carrier molecule is NADP + it transports electrons by accepting & holds 2 high-energy electrons along with a hydrogen ion (H + ). This converts the NADP + into NADPH. The conversion of NADP + into NADPH is one way some of the energy of sunlight can be trapped in chemical form. 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.

9 L IGHT -D EPENDENT R EACTIONS The light-dependent reactions require light. The light-dependent reactions produce oxygen gas and convert ADP and NADP + into the energy carriers ATP and NADPH. Copyright Pearson Prentice Hall

10 2 Photosystems: I & II (Ancient Greek: phos = light and systema = assembly)Greek Each system is identified by its wavelength of light (700 and 680 nanometers, respectively for PSI and PSII in chloroplasts).wavelength nanometersPSIPSII These are functional & structural units of photosynthesis: that deal with the absorption of light and the transfer of energy and electrons.photosynthesisabsorption of lightenergyelectrons They are both found in the thylakoid membranes of chloroplasts for plants, and algae, or in the cytoplasmic membrane of photosynthetic bacteria, such as cyanobacteria.thylakoid membranes Each contain chlorophyll molecules, that can convert light energy into chemical energy.chlorophyll A photon of light causes an electron to reach a high energy level. Both photosystems, the energized electron must be passed to a chlorophyll molecule in the reaction center before it can leave the photosystem. Both contain carotenoid molecules. Electron Transport: notes & FYIs

11 PS I & PS II Photosystem I (PS I) is so named because it was discovered before photosystem II (PSII).photosystem II These discoveries were in the late 20 th century. (1950’s – 1960’s)  Light reactions take place in the ________________ membrane. 1.) PS II - Light excites the electrons in Chlorophyll a 2.) PS II – These electrons move to a primary electron acceptor 3.) PS II – The Electron Transport Chain: transfers these electrons via series of molecules ) PS I – Light excites the electrons in Chlorophyll a – These electrons move to a primary electron acceptor & are replaced by electrons from PS II. 5.) PS I – 2 nd Electron Transport Chain: transfers these electrons & combine with NADP + to make NADPH Another Presentation on Photosynthesis I ( Just another way to see the same material presented.) Another Presentation on Photosynthesis I Photosyn video by kids ( Nice overview !) Photosyn video by kids Calvin Cycle Video ( Your teacher really gets a kick out of this one.) Calvin Cycle Video

12 MORE IMAGES SHOWING PHOTOSYNTHESIS Copyright Pearson Prentice Hall

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15 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall

16 L IGHT -D EPENDENT R EACTIONS Photosynthesis begins when pigments in photosystem II absorb light, increasing their energy level. Copyright Pearson Prentice Hall Photosystem II

17 L IGHT -D EPENDENT R EACTIONS These high-energy electrons are passed on to the electron transport chain. Copyright Pearson Prentice Hall Photosystem II Electron carriers High-energy electron

18 L IGHT -D EPENDENT R EACTIONS Enzymes on the thylakoid membrane break water molecules into: Copyright Pearson Prentice Hall Photosystem II 2H 2 O Electron carriers High-energy electron

19 L IGHT -D EPENDENT R EACTIONS hydrogen ions oxygen atoms energized electrons Copyright Pearson Prentice Hall Photosystem II 2H 2 O + O 2 Electron carriers High-energy electron

20 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall 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

21 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall 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

22 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall 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

23 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall 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

24 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall Photosystem II 2H 2 O High-energy electrons move through the electron transport chain from photosystem II to photosystem I. + O 2 Photosystem I

25 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall 2H 2 O Pigments in photosystem I use energy from light to re-energize the electrons. + O 2 Photosystem I

26 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall 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

27 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall 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

28 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall 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

29 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall 2H 2 O The difference in charges across the membrane provides the energy to make ATP + O 2 2 NADP + 2 NADPH 2

30 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall 2H 2 O H + ions cannot cross the membrane directly. + O 2 ATP synthase 2 NADP + 2 NADPH 2

31 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall 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

32 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall 2H 2 O As H + ions pass through ATP synthase, the protein rotates. + O 2 ATP synthase 2 NADP + 2 NADPH 2

33 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall 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

34 L IGHT -D EPENDENT R EACTIONS Copyright Pearson Prentice Hall 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

35 LIGHT-DEPENDENT REACTIONS The light-dependent reactions use water, ADP, and NADP +. The light-dependent reactions produce oxygen, ATP, and NADPH. These compounds provide the energy to build energy- containing sugars from low-energy compounds.

36 IN THE CALVIN CYCLE ~ LIGHT IN DEPENDENT! ATP and NADPH formed by light-dependent reactions contain an abundance of chemical energy, but they are not stable enough to store that energy for more than a few minutes. During the Calvin cycle plants use the energy that ATP and NADPH contain to build high-energy compounds that can be stored for a long time. The Calvin cycle uses ATP and NADPH from the light- dependent reactions to produce high-energy sugars.

37 T HE C ALVIN C YCLE Six carbon dioxide molecules enter the cycle from the atmosphere and combine with six 5-carbon molecules. Copyright Pearson Prentice Hall CO 2 Enters the Cycle

38 T HE C ALVIN C YCLE The result is twelve 3-carbon molecules, which are then converted into higher-energy forms. Copyright Pearson Prentice Hall

39 T HE C ALVIN C YCLE The energy for this conversion comes from ATP and high-energy electrons from NADPH. Copyright Pearson Prentice Hall 12 NADPH ADP 12 NADP + Energy Input

40 T HE C ALVIN C YCLE Two of twelve 3-carbon molecules are removed from the cycle. Copyright Pearson Prentice Hall Energy Input 12 NADPH ADP 12 NADP +

41 T HE C ALVIN C YCLE The molecules are used to produce sugars, lipids, amino acids and other compounds. Copyright Pearson Prentice Hall 12 NADPH ADP 12 NADP + 6-Carbon sugar produced Sugars and other compounds

42 T HE C ALVIN C YCLE The 10 remaining 3-carbon molecules are converted back into six 5- carbon molecules, which are used to begin the next cycle. Copyright Pearson Prentice Hall 12 NADPH ADP 12 NADP + 5-Carbon Molecules Regenerated Sugars and other compounds 6 6 ADP

43 C HEMIOSMOSIS The diffusion of ions across a selectively-permeable membrane. Primarily relates to the synthesis of ATP by the movement of hydrogen ions across a membrane during cellular respiration. Hydrogen ions (protons) will diffuse from an area of high proton concentration to an area of lower proton concentration. diffuse It’s the diffusion of water across a membrane, that is why it is called chemiosmosis.

44 CARBON FIXATION This is a process that allows gaseous carbon dioxide to convert into a solid compound.carbon dioxide Mostly deals with the photosynthesis processes found in autotrophs (organisms that produce their own food), whereby carbon dioxide is changed into sugars.autotrophscarbon dioxide

45 CALVIN CYCLE This is the most common biological method of carbon fixation. In plants, there are three types of carbon fixation during photosynthesis:plants 1. C 3 C 3 2. C 4 C 4 3. CAM CAM **Next few slides is a conglomerate of information from a variety of sources including wikipedia.wikipedia **Wikipedia, is a like an encyclopedia; however, anyone can edit it.anyone can edit it So, you always have to do back up research to verify the information that you are reading.

46 C 3 C 3 plants that use the Calvin cycle for the initial steps that incorporate CO 2 into organic matter, forming a 3-carbon compound as the first stable. C 4 C 4 plants that preface the Calvin cycle with reactions do incorporate CO 2 into a 4-carbon compound. C4 plants have a distinctive internal leaf anatomy. Tropical grasses, such as sugar cane and maize are C4 plants, but there are many broadleaf plants that are C4. Overall, 7600 species of terrestrial plants use C 4 carbon fixation, representing around 3% of all species. sugar canemaize CAMCAM-plants that use Crassulacean acid metabolism as an adaptation for arid conditions.Crassulacean acid metabolism CO 2 enters through the stomata during the night and is converted into organic acids, which release CO 2 for use in the Calvin cycle during the day, when the stomata are closed.stomata The jade plant ( Crassula ovata ) and cacti are typical of CAM plants Sixteen thousand species of plants use CAM. [3] Crassula ovatacacti [3] A little more about C 3, C 4, & CAM…

47 T HE C ALVIN C YCLE Takes place in the stroma. Steps: 1.) CO2 combines with RuBP to form to molecules of PGA 2.) PGA is converted to PGAL. 3.) Most of PGAL is converted back to RuBP. (Some PGAL is used to make organic compounds.) RuBP – Ribulose-1,5-bisphosphate (5 Carbon Molecule) used in carbon fixing of the Calvin Cycle. PGAL – Phosphoglyceraldehyde (3-Carbon Molecule)Phosphoglyceraldehyde

48 Factors Affecting Photosynthesis Many factors affect the rate of photosynthesis, including: Water Temperature Intensity of light Copyright Pearson Prentice Hall

49 A. thylakoids. B. chloroplasts. C. photosystems. D. chlorophyll. Copyright Pearson Prentice Hall In plants, photosynthesis takes place inside the

50 A. hydrogen ions flowing through an enzyme in the thylakoid membrane. B. transfer of a phosphate from ADP. C. electrons moving through the electron transport chain. D. electrons transferred directly from NADPH. Copyright Pearson Prentice Hall Energy to make ATP in the chloroplast comes most directly from

51 A. ATP. B. high-energy electrons. C. low-energy electrons. D. ADP. Copyright Pearson Prentice Hall NADPH is produced in light-dependent reactions and carries energy in the form of

52 A. light-dependent reactions B. light-independent reactions C. electron transport chain D. photosynthesis Copyright Pearson Prentice Hall What is another name for the Calvin cycle?

53 A. wind B. water supply C. temperature D. light intensity Copyright Pearson Prentice Hall Which of the following factors does NOT directly affect photosynthesis?


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