Comparing Producers and Consumers

Chapter 7 Photosynthesis Sunlight consists of a spectrum of colors, visible here in a rainbow

Photosynthesis: Making of sugar

The Cycling of Energy Producers Photosynthesis (Chloroplast) Glucose Cell Respiration (Mitochondria) ATP Chemical Reactions Consumers Cell Respiration (Mitochondria) ATP Chemical Reactions

Outer Membrane Grana Stroma Starch grain Thylakoid

Lesson 2. 1: Investigating Plants in Light and Dark

How does light affect photosynthesis?

Possible BTB Colors

Making and Explaining Predictions Predicting BTB changes for plants in the light How will plants in the light affect yellow BTB? How will plants in the light affect blue BTB? Explaining your predictions: How do plants in the light affect CO 2 in the air? Predicting BTB changes for plants in the dark How will plants in the dark affect yellow BTB? How will plants in the dark affect blue BTB? Explaining your predictions: How do plants in the dark affect CO 2 in the air?

10 Photo of reactant molecules: CO 2 (carbon dioxide) and H 2 O (water) Start by making the molecules of the reactants and energy units of light. Put them on the reactants side, then rearrange the atoms and energy units to show the products. Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away). Chemical change Reactants Products Water Carbon dioxide

11 Photo of product molecules: H 6 C 12 O 6 (sugar) and O 2 (oxygen) Start by making the molecules and energy units of the reactants and putting them on the reactants side, then rearrange the atoms and energy units to show the products.. Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away). Reactants Products Glucose Oxygen Chemical change

How do glucose water, carbon dioxide and oxygen move for a plant leaf to photosynthesize? water carbon dioxideoxygen glucose

What happens inside the leaf cell as it photosynthesizes? Chemica l change

14 Chemical change Reactants Glucose Oxygen Products Water Light energy Carbon Dioxide Atoms last forever! Energy lasts forever! What happens to atoms and energy in photosynthesis?

Explaining Your Results for Plants in the Light 1.What patterns did you see for color changes in BTB for plants in the light? 2.What can we conclude about CO 2 ? What do plants in the light do to carbon dioxide in the air? 3.How can we explain these results with answers to the Three Questions?

Three facts about matter: 1.Atoms last forever 2.Atoms make up the mass of all materials. 3.Atoms are bonded to other atoms in molecules. Two facts about energy: 1.Energy lasts forever. Energy is never created or destroyed in chemical changes. 2.Energy can be transformed from one form to another. Some common forms of energy include: – Heat – Light – Motion – Chemical energy: energy stored in bonds of molecules

Focusing in on the location of photosynthesis in a plant ThylakoidThylakoid Space Mesophyll cell Mesophyll Vein Stomata CO 2 O2O2 Chloroplast 5 µm 1 µm Outer membrane Intermembrane space Inner membrane Granum Storma Leaf cross section

Tracking atoms through photosynthesis 6 CO 2 12 H 2 O Reactants: Products: C 6 H 12 O 6 6H2O6H2O 6O26O2

Overview of Photosynthesis Photosynthesis can be divided into two stages: Light Reactions and Calvin Cycle –In the light reactions, light energy is converted to chemical energy, which is temporarily stored in ATP and the energy carrier molecule NADPH. –In the Calvin Cycle, organic compounds are formed using CO 2 and the chemical energy stored in ATP and NADPH.

Parts of the Chloroplast

Figure 10.5 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle Light LIGHT REACTIONS Chloroplast H2OH2O

Figure 10.5 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle ATP NADPH O2O2 H2OH2O Light LIGHT REACTIONS Chloroplast

CO 2 CALVIN CYCLE O2O2 [CH 2 O] (sugar) NADP  ADP + P i Figure 10.5 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle H2OH2O Light LIGHT REACTIONS Chloroplast ATP NADPH

Capturing Light Energy Light and Pigments –White light from the sun is composed of an array of colors called the visible spectrum. –Pigments absorb certain colors of light and reflect or transmit the other colors. Chloroplast Pigments –Located in the membrane of the thylakoids of chloroplasts are several pigments, including chlorophylls (such as chlorophyll a and chlorophyll b) and carotenoids.

Figure 10.6 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

Why leaves are green: interaction of light with chloroplasts Light Reflected Light Chloroplast Absorbed light Granum Transmitted light

Pigments and Light Reactions

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Converting Light Energy To Chemical Energy The pigments are grouped in clusters of a few hundred molecules in the thylakoid membrane. Each cluster and the proteins that the pigment molecules are embedded in are referred to collectively as a photosystem. By absorbing light, pigment molecules in photosystem I and photosystem II acquire some of the energy carried by the light. e–e–

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure A mechanical analogy for the light reactions Mill makes ATP e–e– e–e– e–e– e–e– e–e– Photon Photosystem II Photosystem I e–e– e–e– NADPH Photon

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Excitation of isolated chlorophyll by light Excited state Energy of election e–e– Heat Photon (fluorescence) Chlorophyll molecule Ground state Photon (a) Excitation of isolated chlorophyll molecule (b) Fluorescence

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Converting Light Energy To Chemical Energy In each photosystem, the acquired energy is passed quickly to other pigment molecules until it reaches a specific pair of chlorophyll a molecules. The acquired energy forces electrons to enter a higher energy level in the two chlorophyll a molecules of photosystem II. These energized electrons are said to be “excited.” The excited electrons have enough energy to leave the chlorophyll a molecules. The acceptor of these electrons from photosystem II is a molecule called the primary electron acceptor, which donates the electrons to the electron transport chain. As the electrons move from molecule to molecule in this chain, they lose most of the acquired energy. The energy they lose is used to move protons into the thylakoid.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Converting Light Energy To Chemical Energy Making ATP in Light Reactions – An important part of the light reactions is the synthesis of ATP. During chemiosmosis, the movement of protons through ATP synthase into the stroma releases energy, which is used to produce ATP

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Converting Light Energy To Chemical Energy Replacing Electrons in Light Reactions – Electrons from photosystem II replace electrons that leave photosystem I. Replacement electrons for photosystem II are provided by the splitting of water molecules. – Oxygen produced when water molecules are split diffuses out of the chloroplast and then leaves the plant.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 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 O2O2 1 1⁄21⁄2 2 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 +

Light Reactions

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Comparison of chemiosmosis in mitochondria and chloroplasts Key Higher [H + ] Lower [H + ] Mitochondrion Chloroplast MITOCHONDRION STRUCTURE Intermembrance space Membrance Matrix Electron transport chain H+H+ Diffusion Thylakoid space Stroma ATP H+H+ P ADP+ ATP Synthase CHLOROPLAST STRUCTURE

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Calvin Cycle and Carbon Fixation The ATP and NADPH produced in the light reactions drive the second stage of photosynthesis, the Calvin cycle. In the Calvin cycle, CO 2 is incorporated into organic compounds, a process called carbon fixation. The Calvin cycle, which occurs in the stroma of the chloroplast, is a series of enzyme-assisted chemical reactions that produces a three-carbon sugar.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Calvin Cycle and Carbon Fixation The ATP and NADPH produced in the light reactions drive the second stage of photosynthesis, the Calvin cycle. In the Calvin cycle, CO 2 is incorporated into organic compounds, a process called carbon fixation. The Calvin cycle, which occurs in the stroma of the chloroplast, is a series of enzyme-assisted chemical reactions that produces a three-carbon sugar. Most of the three-carbon sugars (G3P) generated in the Calvin cycle are converted to a five-carbon sugar (RuBP) to keep the Calvin cycle operating. But some of the three- carbon sugars leave the Calvin cycle and are used to make organic compounds, in which energy is stored for later use.

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

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

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

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure C 4 and CAM photosynthesis compared Organic acids release CO 2 to Calvin cycle Spatial separation of steps. In C 4 plants, carbon fixation and the Calvin cycle occur in different types of cells. (a) Temporal separation of steps. In CAM plants, carbon fixation and the Calvin cycle occur in the same cells at different times. (b) Pineapple Sugarcane Bundle- sheath cell Mesophyll Cell Organic acid CALVIN CYCLE Sugar CO 2 Organic acid CALVIN CYCLE Sugar C4C4 CAM CO 2 incorporated into four-carbon organic acids (carbon fixation) Night Day 1 2 Organic acids release CO 2 to Calvin cycle CO 2

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chromatography of Plant Pigments Table 1- Chromatography of Plant Pigments Band Number PigmentMigration Distance (mm) R f Value 1 (top) Carotene59 2 Xanthophyll25 3 Chlorophyll a15 4 Chlorophyll b9 - Solvent60

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photosynthesis and the Light Reaction Table 2 - Transmittance Cuvette Time 0 min5 min10 min15 min 2 (Dark) (Unboiled) (Boiled)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Calvin Cycle

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