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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece.

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Presentation on theme: "Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece."— Presentation transcript:

1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 10 Photosynthesis

2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Products of photosynthesis create ecosystems.

3 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photosynthesis Photosynthesis is summarized as 6 CO H 2 O + Light energy C 6 H 12 O O H 2 O

4 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An overview of photosynthesis H2OH2O CO 2 Light LIGHT REACTIONS CALVIN CYCLE Chloroplast [CH 2 O] (sugar) NADPH NADP ADP + P O2O2 Figure 10.5 ATP

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6 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Quiz What is the summary equation for photosynthesis? Where does the light energy go? What role does Oxygen play in Cellular Respiration?

7 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Quiz What is the summary equation for photosynthesis? 3 points Where does the light energy go? 3 Points Bonds in glucose What role does Oxygen play in Cellular Respiration? (2 points) accepts H + to form H 2 O 6 CO H 2 O + Light energy C 6 H 12 O O H 2 O

8 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 10.2 Light reactions The light reactions convert solar energy to the chemical energy of ATP and NADPH. – Harness energy in light

9 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The electromagnetic spectrum Gamma rays X-raysUVInfrared Micro- waves Radio waves 10 –5 nm 10 –3 nm 1 nm 10 3 nm 10 6 nm 1 m 10 6 nm 10 3 m nm Visible light Shorter wavelength Higher energy Longer wavelength Lower energy Figure 10.6

10 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photosynthetic Pigments: The Light Receptors

11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

12 Chlorophyll a – Is the main photosynthetic pigment Chlorophyll b, Carotenoids – Are accessory pigments

13 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Excitation of Chlorophyll by Light When a pigment absorbs light – It goes from a ground state to an excited state, which is unstable Excited state Energy of election Heat Photon (fluorescence) Chlorophyll molecule Ground state Photon e–e– Figure A

14 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A photosystem – Is composed of a reaction center surrounded by a number of light- harvesting complexes Primary election acceptor Photon Thylakoid Light-harvesting complexes Reaction center Photosystem STROMA Thylakoid membrane Transfer of energy Special chlorophyll a molecules Pigment molecules THYLAKOID SPACE (INTERIOR OF THYLAKOID) Figure e–e–

15 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The light-harvesting complexes – Consist of pigment molecules bound to particular proteins – Funnel the energy of photons of light to the reaction center

16 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings When a reaction-center chlorophyll molecule absorbs energy – One of its electrons gets bumped up to a primary electron acceptor The thylakoid membrane – Is populated by two types of photosystems, I (P700) and II (P680)

17 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Noncyclic Electron Flow Noncyclic electron flow – Is the primary pathway of energy transformation in the light reactions. – Produces NADPH, ATP and O 2.

18 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings H2OH2OCO 2 Light LIGHT REACTIONS CALVIN CYCLE O2O2 NADP + ADP ATP NADPH [CH 2 O] (sugar) Light Photosystem II (PS II) e P680 1 Energy of electrons

19 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings H2OH2OCO 2 Light LIGHT REACTIONS CALVIN CYCLE O2O2 NADP + NADPH [CH 2 O] (sugar) Light Photosystem II (PS II) e Primary acceptor ADP ATP 2 H + + O2O2 1 2 H2OH2O e e Energy of electrons P680

20 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 1 3 O2O2 + H2OH2OCO 2 Light LIGHT REACTIONS CALVIN CYCLE O2O2 NADP + NADPH [CH 2 O] (sugar) Light Photosystem II (PS II) e Primary acceptor ATP 2 H H2OH2O 2 Energy of electrons ADP Pq Cytochrome complex Pc ATP Electron transport chain 5 4 P680 e e

21 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings O2O2 H2OH2O CO 2 Light LIGHT REACTIONS CALVIN CYCLE O2O2 NADPH [CH 2 O] (sugar) Light Photosystem II (PS II) e Primary acceptor 2 H H2OH2O 2 Energy of electrons ADP Pq Cytochrome complex Pc ATP Electron transport chain 5 NADP + ATP e Photosystem I (PS I) Light P680 P700 + e e

22 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings P700 + CO 2 Photosystem II (PS II) H2OH2O Light LIGHT REACTIONS CALVIN CYCLE O2O2 NADPH [CH 2 O] (sugar) e Primary acceptor 2 H H2OH2O e e 1 Energy of electrons Pq Cytochrome complex Pc ATP Electron transport chain NADP + Primary acceptor e Photosystem I (PS I) Light ADP ATP 5 Fd Electron Transport chain 7 NADP + reductase NADPH NADP H H P680 O2O2 e e

23 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cyclic Electron Flow Under certain conditions – Photoexcited electrons take an alternative path. – This involves only PSI and short circuits the system. But, does produce one ATP

24 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The light reactions and chemiosmosis: the organization of the thylakoid membrane LIGHT REACTOR NADP + ADP ATP NADPH CALVIN CYCLE [CH 2 O] (sugar) STROMA (Low H + concentration) Photosystem II LIGHT H2OH2O CO 2 Cytochrome complex O2O2 H2OH2O O2O Photosystem I Light THYLAKOID SPACE (High H + concentration) STROMA (Low H + concentration) Thylakoid membrane ATP synthase Pq Pc Fd NADP + reductase NADPH + H + NADP + + 2H + To Calvin cycle ADP P ATP 3 H+H+ 2 H + +2 H + 2 H + Figure 10.17

25 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Homework Read and outline C 10. Pp ( )

26 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An elegant experiment by Engelmann Illuminated a filament of green algae on a microscope slide using a prism to break up the light. Included an aerobic bacterium. Observed where the bacteria congregated. – They need O 2 and will move towards it.

27 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Englemanns results. Where are the bacteria congregating? Why? What does that tell us.

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29 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Quiz What carbohydrate is produced directly from the Calvin Cycle? What are the three phases of the Calvin cycle? Where does O 2 come from? What molecule?

30 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Quiz What carbohydrate is produced directly from the Calvin Cycle? (2 Points) Glyceraldehyde 3- phosphate (or G3P) What are the three phases of the Calvin cycle? (3 points) Carbon Fixation, Reduction, Regeneration of RuBP What part of Photosynthsis generates O 2 from? What molecule? (2 Points) Light Reactions, H 2 O

31 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 10.3 The Calvin Cycle The Calvin cycle – Is similar to the citric acid cycle (but in reverse) – Occurs in the stroma – Uses the products from the light reactions – Is light independent.

32 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Calvin Cycle Three phases – Carbon fixation – Reduction – Regeneration of the CO 2 acceptor

33 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview of the Calvin Cycle

34 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Think of it this way… 6 simultaneous turns of the Calvin cycle – 6 CO 2 s are fixed by 6 molecules of RuBP 2 G3Ps pop out (2 x 3Cs = 6 Cs) – 1 molecule of Glucose (6C ÷ 6C = 1) 10 G3Ps go to reform RuBP (10x3Cs = 30Cs) – 6 molecules (30Cs ÷ 5Cs = 6) of RuBP.

35 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The Calvin cycle Light H2OH2O CO 2 LIGHT REACTIONS ATP NADPH NADP + [CH 2 O] (sugar) CALVIN CYCLE ADP (Entering one at a time) CO 2 3 Phase 1: Carbon fixation Rubisco Short-lived intermediate 3 PP P Ribulose bisphosphate (RuBP) P 3-Phosphoglycerate 6 ATP 6 ADP Input CALVIN CYCLE O2O2 6

36 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The Calvin cycle (Entering one at a time) CO 2 3 Phase 1: Carbon fixation Rubisco Short-lived intermediate 3 PP P Ribulose bisphosphate (RuBP) P 3-Phosphoglycerate P6 P 1,3-Bisphosphoglycerate 6 NADPH 6 NADP + 6 P i P 6 Glyceraldehyde-3-phosphate (G3P) Phase 2: Reduction 6 ATP CALVIN CYCLE P 1 G3P (a sugar) Output Glucose and other organic compounds 6 ADP Input Light H2OH2O CO 2 LIGHT REACTIONS ATP NADP + [CH 2 O] (sugar) CALVIN CYCLE NADPH ADP O2O2 6

37 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The Calvin cycle (Entering one at a time) CO 2 3 Phase 1: Carbon fixation Rubisco Short-lived intermediate 3 P P P Ribulose bisphosphate (RuBP) P 3-Phosphoglycerate P 6 P 1,3-Bisphosphoglycerate 6 NADPH 6 NADP + 6 P i P 6 Glyceraldehyde-3-phosphate (G3P) Phase 2: Reduction 6 ATP 3 ATP 3 ADP CALVIN CYCLE P 5 Phase 3: Regeneration of the CO 2 acceptor (RuBP) P 1 G3P (a sugar) Output Glucose and other organic compounds G3P 6 ADP Light H2OH2O CO 2 LIGHT REACTIONS NADPH NADP + [CH 2 O] (sugar) CALVIN CYCLE Input ATP ADP O2O2 6

38 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Alternative mechanisms of Carbon fixation On hot, dry days, plants close their stomata – Conserving water – Limits CO 2 – Light reactions continue Causing oxygen to build up Rubisco preferentially binds O 2. Uses ATP w/out replacement. Decreases photosynthetic output.

39 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Leaf Anatomy (See p 725 for more details) Upper Epidermis Cuticle Mesophyll Vein Lower Epidermis Stomate

40 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings C 4 Plants C 4 plants minimize the cost of photorespiration – By incorporating CO 2 into four carbon compounds in mesophyll cells. – PEP Carboxylase to fix CO 2. Forms Oxaloacetate Moved to Bundle sheath cells – Calvin cycle occurs. Spatial separation of light and dark reactions.

41 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings C 4 leaf anatomy and the C 4 pathway CO 2 Mesophyll cell Bundle- sheath cell Vein (vascular tissue) Photosynthetic cells of C 4 plant leaf Stoma Mesophyll cell C 4 leaf anatomy PEP carboxylase Oxaloacetate (4 C) PEP (3 C) Malate (4 C) ADP ATP Bundle- Sheath cell CO 2 Pyruate (3 C) CALVIN CYCLE Sugar Vascular tissue Figure CO 2

42 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CAM Plants CAM plants – Open their stomata at night, incorporating CO 2 into organic acids. During the day, the stomata close – And the CO 2 is released from the organic acids for use in the Calvin cycle. Temporal separation of Light and Dark reactions.

43 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The CAM pathway is similar to the C4 pathway

44 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Importance of Photosynthesis: A Review A review of photosynthesis Light reactions: Are carried out by molecules in the thylakoid membranes Convert light energy to the chemical energy of ATP and NADPH Split H 2 O and release O 2 to the atmosphere Calvin cycle reactions: Take place in the stroma Use ATP and NADPH to convert CO 2 to the sugar G3P Return ADP, inorganic phosphate, and NADP+ to the light reactions O2O2 CO 2 H2OH2O Light Light reaction Calvin cycle NADP + ADP ATP NADPH + P 1 RuBP 3-Phosphoglycerate Amino acids Fatty acids Starch (storage) Sucrose (export) G3P Photosystem II Electron transport chain Photosystem I Chloroplast Figure 10.21

45 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Homework Read Enzyme lab (#2) In your lab book. – Pre-lab tomorrow. Exam on Monday C-7-10 Finish review given out last week, do self quizzes and review quizzes on CD, think of potential essay questions!


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