LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 10 Photosynthesis Lectures by Erin Barley Kathleen Fitzpatrick 2011 Pearson Education, Inc.
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Photosynthesis & Cell Respiration
2011 Pearson Education, Inc.
Big Ideas 2.A.1) All living systems require constant input of free energy. 2.A.2) Organisms capture and store free energy for use in biological processes. 2011 Pearson Education, Inc. Illustrative Examples: Glycolysis Krebs cycle Calvin cycle Fermentation Chemiosmosis
Big Ideas 2.A.1) All living systems require constant input of free energy. 2.A.2) Organisms capture and store free energy for use in biological processes. Illustrative Examples: Inquiry section (Fig. 10.10) Be able to explain the expt. and conclusion. 2011 Pearson Education, Inc.
Figure 10.9 TECHNIQUE White light Refracting prism Chlorophyll solution Photoelectric tube Galvanometer Slit moves to pass light of selected wavelength. Green light High transmittance (low absorption): Chlorophyll absorbs very little green light. Blue light Low transmittance (high absorption): Chlorophyll absorbs most blue light.
Rate of photosynthesis (measured by O 2 release) Absorption of light by chloroplast pigments Figure 10.10 RESULTS Chlorophyll a Chlorophyll b Carotenoids (a) Absorption spectra 400 500 600 700 Wavelength of light (nm) (b) Action spectrum 400 500 600 700 Aerobic bacteria Filament of alga (c) Engelmann s experiment 400 500 600 700
Beyond the Scope of the AP Exam Memorization of: the steps in the Calvin cycle and the structure of the molecules and the names of enzymes (with the exception of ATP synthase). memorization of the steps in glycolysis and the Krebs cycle, or of the structures of the molecules the names of the specific electron carriers in the ETC 2011 Pearson Education, Inc.
Overview: The Process That Feeds the Biosphere Photosynthesis is the process that converts solar energy into chemical energy Directly or indirectly, photosynthesis nourishes almost the entire living world 2011 Pearson Education, Inc.
1 2 Video Notes: Please use the back of the Photosynthesis Chart.
2011 Pearson Education, Inc. BioFlix: Photosynthesis
Mix & Match Review: Ch. 10.1-2 1. Chloroplast (plastid) 2. Stomata 3. Thylakoids 4. Stroma 1, 4, 7 1. Chlorophyll a, b 2. Light Reactions (Part 1) 3. Calvin Cycle (Part 2) 4. Pigments 2, 5, 8 1. Water 2. Sugar 3. Oxygen 4. NADPH 3, 6
Photosynthesis: Two Factory Model Light-Dependent Reactions Light Independent Reactions 1) Sunlight energy is trapped, turned into ATP. 2) Water is split into O, H, and electrons. 3) These e - s are grabbed by carrier molecules for later use and 0 2 is flushed. 1) ATP powers the manufacture of glucose using carbon dioxide molecules. 2) At the same time electrons are grabbed and used to make sugar.
Photosynthesis occurs in plants, algae, certain other protists, and some prokaryotes These organisms feed not only themselves but also most of the living world 2011 Pearson Education, Inc.
Figure 10.2 (a) Plants (b) Multicellular alga (c) Unicellular protists 10 m (d) Cyanobacteria 40 m (e) Purple sulfur bacteria 1 m
Lecture Outline 1. Photosynthesis converts light energy to the chemical energy of food. 2. The light reactions convert solar energy to the chemical energy of ATP and NADPH. 3. The Calvin Cycle uses chemical energy of ATP and NADPH to reduce (give e - s) to sugar. 4. Other mechanisms that fix carbon have evolved in hot, arid climates. 2011 Pearson Education, Inc.
Concept #1: Photosynthesis converts light energy to the chemical energy of food Chloroplasts are structurally similar to and likely evolved from photosynthetic bacteria The structural organization of these cells allows for the chemical reactions of photosynthesis 2011 Pearson Education, Inc.
Figure 10.4 Leaf cross section Chloroplasts Vein Mesophyll Stomata CO 2 O 2 Chloroplast Mesophyll cell Stroma Thylakoid Granum Thylakoid space Outer membrane Intermembrane space Inner membrane 20 m 1 m
Figure 10.4a Leaf cross section Chloroplasts Vein Mesophyll Stomata CO 2 O 2 Chloroplast Mesophyll cell 20 m
Figure 10.4b Chloroplast Stroma Thylakoid Granum Thylakoid space Outer membrane Intermembrane space Inner membrane 1 m
Figure 10.4c Mesophyll cell 20 m
Figure 10.4d Stroma Granum 1 m
The Two Stages of Photosynthesis: A Preview Photosynthesis consists of the light reactions (the photo part) and Calvin cycle (the synthesis part) The light reactions (in the thylakoids) Split H 2 O Release O 2 Reduce NADP + to NADPH Generate ATP from ADP by photophosphorylation 2011 Pearson Education, Inc.
The Calvin cycle (in the stroma) forms sugar from CO 2, using ATP and NADPH The Calvin cycle begins with carbon fixation, incorporating CO 2 into organic molecules 2011 Pearson Education, Inc.
Figure 10.6-1 H 2 O Light NADP ADP + P i Light Reactions Chloroplast
Figure 10.6-2 H 2 O Light NADP ADP + P i Light Reactions ATP NADPH Chloroplast O 2
Figure 10.6-3 H 2 O CO 2 Light Light Reactions NADP ADP + P i ATP NADPH Calvin Cycle Chloroplast O 2
Figure 10.6-4 H 2 O CO 2 Light Light Reactions NADP ADP + P i ATP NADPH Calvin Cycle Chloroplast O 2 [CH 2 O] (sugar)
Stage CO 2 H 2 O Light C 6 H 12 O 6 6O 2 Light Dependent Reactions (PSII & PSI) Light Independent Reactions (Calvin Cycle) Totals 2011 Pearson Education, Inc.
Lecture Outline 1. Photosynthesis converts light energy to the chemical energy of food. 2. The light reactions convert solar energy to the chemical energy of ATP and NADPH. 3. The Calvin Cycle uses chemical energy of ATP and NADPH to reduce (give e - s) to sugar. 4. Other mechanisms that fix carbon have evolved in hot, arid climates. 2011 Pearson Education, Inc.
Concept #2: The light reactions convert solar energy to the chemical energy of ATP and NADPH Chloroplasts are solar-powered chemical factories Their thylakoids transform light energy into the chemical energy of ATP and NADPH 2011 Pearson Education, Inc.
Figure 10.7 1 m 10 5 nm 10 3 nm 1 nm 10 3 nm 10 6 nm (10 9 nm) 10 3 m Gamma rays X-rays UV Infrared Microwaves Radio waves Visible light 380 450 500 550 600 650 700 750 nm Shorter wavelength Higher energy Longer wavelength Lower energy
Photosynthetic Pigments: The Light Receptors Pigments are substances that absorb visible light Different pigments absorb different wavelengths Wavelengths that are not absorbed are reflected or transmitted Leaves appear green because chlorophyll reflects and transmits green light 2011 Pearson Education, Inc.
Animation: Light and Pigments Right-click slide / select Play 2011 Pearson Education, Inc.
Figure 10.8 Light Reflected light Chloroplast Absorbed light Granum Transmitted light
A spectrophotometer measures a pigment s ability to absorb various wavelengths This machine sends light through pigments and measures the fraction of light transmitted at each wavelength 2011 Pearson Education, Inc.
Figure 10.9 TECHNIQUE White light Refracting prism Chlorophyll solution Photoelectric tube Galvanometer Slit moves to pass light of selected wavelength. Green light High transmittance (low absorption): Chlorophyll absorbs very little green light. Blue light Low transmittance (high absorption): Chlorophyll absorbs most blue light.
Rate of photosynthesis (measured by O 2 release) Absorption of light by chloroplast pigments Figure 10.10 RESULTS Chlorophyll a Chlorophyll b Carotenoids (a) Absorption spectra 400 500 600 700 Wavelength of light (nm) (b) Action spectrum 400 500 600 700 Aerobic bacteria Filament of alga (c) Engelmann s experiment 400 500 600 700
Chlorophyll a is the main photosynthetic pigment Accessory pigments, such as chlorophyll b, broaden the spectrum used for photosynthesis Accessory pigments called carotenoids absorb excessive light that would damage chlorophyll 2011 Pearson Education, Inc.
Figure 10.11 CH 3 CH 3 in chlorophyll a CHO in chlorophyll b Porphyrin ring Hydrocarbon tail (H atoms not shown) Hydrophobic and easily dissolve Into cell membrane
Excitation of Chlorophyll by Light When a pigment absorbs light, it goes from a ground state to an excited state, which is unstable When excited electrons fall back to the ground state, photons are given off, an afterglow called fluorescence If illuminated, an isolated solution of chlorophyll will fluoresce, giving off light and heat 2011 Pearson Education, Inc.
Figure 10.12 Energy of electron e Excited state Heat Photon Chlorophyll molecule Photon (fluorescence) Ground state (a) Excitation of isolated chlorophyll molecule (b) Fluorescence
A Photosystem: A Reaction-Center Complex Associated with Light-Harvesting Complexes A photosystem consists of a reaction-center complex (a type of protein complex) surrounded by light-harvesting complexes The light-harvesting complexes (pigment molecules bound to proteins) transfer the energy of photons to the reaction center 2011 Pearson Education, Inc.
Thylakoid membrane Figure 10.13b Chlorophyll STROMA Protein subunits THYLAKOID SPACE (b) Structure of photosystem II
Thylakoid membrane Figure 10.13a Photon Lightharvesting complexes Photosystem Reactioncenter complex STROMA Primary electron acceptor 1 e Transfer of energy Special pair of chlorophyll a molecules (a) How a photosystem harvests light Pigment molecules THYLAKOID SPACE (INTERIOR OF THYLAKOID)
Thylakoid membrane Figure 10.13a Photon Lightharvesting complexes Photosystem Reactioncenter complex STROMA Primary electron acceptor e Transfer of energy 2 Special pair of chlorophyll a molecules (a) How a photosystem harvests light Pigment molecules THYLAKOID SPACE (INTERIOR OF THYLAKOID)
Thylakoid membrane Figure 10.13a Photon Lightharvesting complexes Photosystem Reactioncenter complex STROMA Primary electron acceptor e 3 Transfer of energy Special pair of chlorophyll a molecules (a) How a photosystem harvests light Pigment molecules THYLAKOID SPACE (INTERIOR OF THYLAKOID)
A primary electron acceptor in the reaction center accepts excited electrons and is reduced as a result Solar-powered transfer of an electron from a chlorophyll a molecule to the primary electron acceptor is the first step of the light reactions 2011 Pearson Education, Inc.
There are two types of photosystems in the thylakoid membrane: PSII and PSI Photosystem II (PS II) functions first (the numbers reflect order of discovery) and is best at absorbing a wavelength of 680 nm The reaction-center chlorophyll a of PS II is called P680 2011 Pearson Education, Inc.
Photosystem I (PS I) is best at absorbing a wavelength of 700 nm The reaction-center chlorophyll a of PS I is called P700 2011 Pearson Education, Inc.
Figure 10.14-5 2 H + 1 / 2 O 2 H 2 O 3 e e Primary acceptor e 2 P680 Pq Cytochrome complex 5 4 Pc Primary acceptor e P700 Fd e e 7 8 NADP reductase Light NADP + H NADPH 1 Light 6 ATP Photosystem II (PS II) Pigment molecules Photosystem I (PS I)
Linear Electron Flow During the light reactions, there are two possible routes for electron flow: cyclic and linear Linear electron flow, the primary pathway, involves both photosystems and produces ATP and NADPH using light energy 2011 Pearson Education, Inc.
Figure 10.14-2 Primary acceptor 2 H + 1 / 2 O 2 3 H 2 O e e e 2 P680 1 Light Pigment molecules Photosystem II (PS II)
Figure 10.14-3 2 H + 1 / 2 O 2 H 2 O 3 e e Primary acceptor e 2 Pq 4 Cytochrome complex Pc P680 5 1 Light ATP Pigment molecules Photosystem II (PS II)
Figure 10.14-4 2 H + 1 / 2 O 2 H 2 O 3 e e Primary acceptor e 2 P680 Pq Cytochrome complex 5 4 Pc Primary acceptor e P700 Light 1 Light 6 ATP Photosystem II (PS II) Pigment molecules Photosystem I (PS I)
Figure 10.14-5 2 H + 1 / 2 O 2 H 2 O 3 e e Primary acceptor e 2 P680 Pq Cytochrome complex 5 4 Pc Primary acceptor e P700 Fd e e 7 8 NADP reductase Light NADP + H NADPH 1 Light 6 ATP Photosystem II (PS II) Pigment molecules Photosystem I (PS I)
Figure 10.15 e e Mill makes ATP e e e e NADPH e ATP Photosystem II Photosystem I
Cyclic Electron Flow Cyclic electron flow uses only photosystem I and produces ATP, but not NADPH No oxygen is released Cyclic electron flow generates surplus ATP, satisfying the higher demand in the Calvin cycle 2011 Pearson Education, Inc.
What Linear to Electron do with Flowelectrons? Cyclic Two Electron Things Flow Goal: take in light, e- from water to make energy rich ATP, NADPH Newer photosystem Starts @ PSII (680), splits water, bumps 2e-s with light energy Produces bubbles (O 2 ) ETC: transfers e-s down gradient to PSI (700) (linearly) and makes ATP via chemiosmosis and NADPH Goal: take in light, boost e- to make energy rich ATP Older photosystem Starts @ PSI (700) bumps 2es with light energy to primary acceptor ETC: transfers e-s down gradient to PSI and makes ATP via chemiosmosis Electrons return (cyclically) to rxn center, waiting next photon boost
Stage CO 2 H 2 O Light C 6 H 12 O 6 6O 2 Light Dependent Reactions (PSII & PSI) Light Independent Reactions (Calvin Cycle) 6 photons 6 Totals 6 6 2011 Pearson Education, Inc.
Figure 10.18 STROMA (low H concentration) Photosystem II Light 4 H + Cytochrome complex Light Photosystem I Fd NADP reductase 3 NADP + H Pq NADPH H 2 O 1 THYLAKOID SPACE (high H concentration) 1 / 2 O 2 +2 H + 2 4 H + Pc To Calvin Cycle STROMA (low H concentration) Thylakoid membrane ATP synthase ADP + P i H + ATP
Lecture Outline 1. Photosynthesis converts light energy to the chemical energy of food. 2. The light reactions convert solar energy to the chemical energy of ATP and NADPH. 3. The Calvin Cycle uses chemical energy of ATP and NADPH to reduce (give e - s) to sugar. 4. Other mechanisms that fix carbon have evolved in hot, arid climates. 2011 Pearson Education, Inc.
Mix & Match Review: Ch. 10.3-4 1. Carbon fixation 2. Reduction 3. Regeneration 1, 4, 7 1. Photorespiration 2. CAM 3. C4 2, 5, 8 1. Rubisco 2. Mesophyll cells 3. Bundle sheath cells 3, 6
Concept #3: The Calvin cycle uses the chemical energy of ATP and NADPH to reduce CO 2 to sugar The Calvin cycle, like the citric acid cycle, regenerates its starting material after molecules enter and leave the cycle The cycle builds sugar from smaller molecules by using ATP and the reducing power of electrons carried by NADPH 2011 Pearson Education, Inc.
Carbon enters the cycle as CO 2 and leaves as a sugar named glyceraldehyde 3-phospate (G3P) 2011 Pearson Education, Inc.
Stage CO 2 H 2 O Light C 6 H 12 O 6 6O 2 Light Dependent Reactions (PSII & PSI) Light Independent Reactions (Calvin Cycle) 6 photons 6 6 1 Totals 6 6 1 6 2011 Pearson Education, Inc.
Three cycles (taking in 3 molecules of CO 2 each) will produce one G3P. 2 G3Ps = 1 glucose (for a total of 6 cycles) The Calvin cycle has three phases Carbon fixation (catalyzed by rubisco) Reduction Regeneration of the CO 2 acceptor (RuBP) 2011 Pearson Education, Inc.
Light-Independent Reactions (AKA Dark Rxns) Calvin-Benson Cycle (Stroma) Goal: Produce one glucose Steps: 1.Carboxylation: 3 CO2 + 3RUBP = 6 PGA Key Enzyme: Rubisco 2. Reduction 3. Regeneration 4. Carb. Synthesis
Light-Independent Reactions (AKA Dark Rxns) Calvin-Benson Cycle (Stroma) Goal: Produce one glucose Steps: 1. Carboxylation 2. Reduction: 6 PGA + 6 ATP, 6 NADPH -> 5 G3P ( & 1 G3P that exits cycle) 3. Regeneration 4. Carb. Synthesis
Light-Independent Reactions (AKA Dark Rxns) Calvin-Benson Cycle (Stroma) Goal: Produce one glucose Steps: 1. Carboxylation 2. Reduction 3. Regeneration: 3 ATP + 5 G3P-> 3 RUBP (brings things back to the start) 4. Carb. Synthesis
Light-Independent Reactions (AKA Dark Rxns) Calvin-Benson Cycle (Stroma) Goal: Produce one glucose Steps: 1. Carboxylation 2. Reduction 3. Regeneration 4. Carb. Synthesis: Extra G3P used to make glucose (6C sugar) Note: It takes two turns to make a single sugar: 2 x 3C = 6C
Review: Light-Independent (AKA Dark Reactions or Calvin (Benson) Cycle) ATP donates energy NADPH donates electrons (and carries H along for the ride) CO 2 donates carbon for the sugar backbone Glucose (C 6 H 12 O 6 ) is assembled after two cycles
Stage CO 2 H 2 O Light C 6 H 12 O 6 6O 2 Light Dependent Reactions (PSII & PSI) Light Independent Reactions (Calvin Cycle) 6 photons 6 6 1 Totals 6 6 1 6 2011 Pearson Education, Inc.
Lecture Outline 1. Photosynthesis converts light energy to the chemical energy of food. 2. The light reactions convert solar energy to the chemical energy of ATP and NADPH. 3. The Calvin Cycle uses chemical energy of ATP and NADPH to reduce (give e - s) to sugar. 4. Other mechanisms that fix carbon have evolved in hot, arid climates. 2011 Pearson Education, Inc.
Figure 10.4a Leaf cross section Chloroplasts Vein Mesophyll Stomata CO 2 O 2 Chloroplast Mesophyll cell 20 m
Concept #4: Alternative mechanisms of carbon fixation have evolved in hot, arid climates On hot, dry days, plants close stomata. This conserves H 2 O but also limits photosynthesis The closing of stomata reduces access to CO 2 and causes O 2 to build up These conditions favor an apparently wasteful process called photorespiration 2011 Pearson Education, Inc.
Bottom Line All plants get CO 2 through stomata but lose water through them. Therefore, stomata close in hot, dry times. Plants want to conserve H 2 O, but there is a tension. Plants need CO 2 to do photosynthesis. Dilemma: How to conserve water, yet have enough CO2 for carbon fixation? Closed: Keeps water; no new CO 2 Open: Loses water; gets new CO 2 http://gcte-focus1.org/activities/activity_13/task_133/basin/tutorial/gifs_2/stomata.jpg
Photorespiration Rubisco 2011 Pearson Education, Inc.
Photorespiration Rubisco 2011 Pearson Education, Inc.
Figure 10.20 C 4 leaf anatomy The C 4 pathway Photosynthetic cells of C 4 plant leaf Mesophyll cell Bundlesheath cell Vein (vascular tissue) Mesophyll cell PEP carboxylase Oxaloacetate (4C) Malate (4C) PEP (3C) ADP ATP CO 2 Stoma Bundlesheath cell CO 2 Pyruvate (3C) Calvin Cycle Sugar Vascular tissue
Figure 10.20a C 4 leaf anatomy Photosynthetic cells of C 4 plant leaf Mesophyll cell Bundlesheath cell Vein (vascular tissue) Stoma
Figure 10.20b The C 4 pathway Mesophyll cell PEP carboxylase CO 2 Oxaloacetate (4C) Malate (4C) PEP (3C) ADP ATP Bundlesheath cell CO 2 Pyruvate (3C) Calvin Cycle Sugar Vascular tissue
C 4 Plants Figure 10.20b The C 4 pathway Mesophyll cell PEP carboxylase 1 CO 2 1. Opens stomata at night to get CO 2 2. Closes stomata during day to keep water 3. Fixes (stores) CO 2 as Oxaloacetic Acid (OAA) within mesophyll cell 4. Mesophyll cells not permeable to Rubisco. 1. Why does this matter? 5. Later on (during the day), OAA releases CO 2 that enters Calvin Cycle -> 2011 Pearson glucose Education, Inc. Oxaloacetate (4C) Bundlesheath cell Malate (4C) CO 2 PEP (3C) ADP Pyruvate (3C) Sugar Vascular tissue Calvin Cycle ATP
Figure 10.20b The C 4 pathway C 4 Plants Mesophyll cell PEP carboxylase 2 CO 2 1. Opens stomata at night to get CO 2 2. Closes stomata during day to keep water 3. Fixes (stores) CO 2 as Oxaloacetic Acid (OAA) within mesophyll cell 4. Mesophyll cells not permeable to Rubisco. 1. Why does this matter? 5. Later on (during the day), OAA releases CO 2 that enters Calvin Cycle -> 2011 Pearson Education, Inc. Oxaloacetate (4C) Bundlesheath cell Malate (4C) CO 2 PEP (3C) ADP Pyruvate (3C) Sugar Vascular tissue Calvin Cycle ATP
C 4 Plants Figure 10.20b 1. Opens stomata at night to get CO 2 2. Closes stomata during day to keep water 3. Fixes (stores) CO 2 as Oxaloacetic Acid (OAA) within mesophyll cell 4. Mesophyll cells not permeable to Rubisco. 1. Why does this matter? 5. Later on (during the day), OAA releases CO 2 that enters Calvin Cycle -> 2011 Pearson glucose Education, Inc. The C 4 pathway Mesophyll cell PEP carboxylase Oxaloacetate (4C) Bundlesheath cell Malate (4C) 3 CO 2 PEP (3C) ADP Pyruvate (3C) Sugar Vascular tissue Calvin Cycle ATP 4 CO 2
C 4 Plants 1. Opens stomata at night to get CO 2 2. Closes stomata during day to keep water 3. Fixes (stores) CO 2 as Oxaloacetic Acid (OAA) within mesophyll cell 4. Mesophyll cells not permeable to Rubisco. 1. Why does this matter? 5. Later on (during the day), OAA releases CO 2 that enters Calvin Cycle -> glucose 2011 Pearson Education, Inc. Figure 10.20b The C 4 pathway Mesophyll cell PEP carboxylase Oxaloacetate (4C) Bundlesheath cell Malate (4C) 5 5 CO 2 PEP (3C) ADP Pyruvate (3C) Sugar Vascular tissue Calvin Cycle ATP CO 2
Figure 10.21 C4: Spatial Separation CAM: Time Separation Sugarcane Pineapple C 4 CO2 CAM CO 2 Mesophyll cell Organic acid 1 CO 2 incorporated (carbon fixation) Organic acid Night CO 2 CO 2 Bundlesheath cell Calvin Cycle 2 CO 2 released to the Calvin cycle Calvin Cycle Day Sugar (a) Spatial separation of steps Sugar (b) Temporal separation of steps
Figure 10.21 1. Opens stomata at night (cooler) to get CO 2, keep water CAM: Time Separation 2. Fixes (stores) CO 2 as maltic acid at night Sugarcane C 3. Later on (during 4 the Bundlesheath cell Calvin Cycle CO2 day), maltic acid Mesophyll Organic acid releases cell CO 2 that enters Calvin Cycle - CO >glucose 2 1 2 Pineapple CAM Organic acid CO 2 Calvin Cycle CO 2 1 Night Day Sugar (a) Spatial separation of steps Sugar (b) Temporal separation of steps
Figure 10.21 1. Opens stomata at night (cooler) to get CO 2, keep water CAM: Time Separation 2. Fixes (stores) CO 2 as maltic acid at night Sugarcane C 3. Later on (during 4 the Bundlesheath cell Calvin Cycle CO2 day), maltic acid Mesophyll Organic acid releases cell CO 2 that enters Calvin Cycle - CO >glucose 2 1 2 Pineapple 2 CAM Organic acid CO 2 Calvin Cycle CO 2 Night Day Sugar (a) Spatial separation of steps Sugar (b) Temporal separation of steps
Figure 10.21 1. Opens stomata at night (cooler) to get CO 2, keep water CAM: Time Separation 2. Fixes (stores) CO 2 as maltic acid at night Sugarcane C 3. Later on (during 4 the CO2 day), maltic acid Mesophyll Organic acid releases cell CO 2 that enters Calvin Cycle - CO >glucose 2 Bundlesheath cell Calvin Cycle 1 2 Pineapple CAM Organic acid 3 CO 2 Calvin Cycle CO 2 Night Day Sugar (a) Spatial separation of steps Sugar (b) Temporal separation of steps
The Importance of Photosynthesis: A Review The energy entering chloroplasts as sunlight gets stored as chemical energy in organic compounds Sugar made in the chloroplasts supplies chemical energy and carbon skeletons to synthesize the organic molecules of cells Plants store excess sugar as starch in structures such as roots, tubers, seeds, and fruits In addition to food production, photosynthesis produces the O 2 in our atmosphere 2011 Pearson Education, Inc.
Figure 10.22 H 2 O CO 2 Light Light Reactions: Photosystem II Electron transport chain Photosystem I Electron transport chain NADP ADP + P i RuBP ATP NADPH 3-Phosphoglycerate Calvin Cycle G3P Starch (storage) Chloroplast O 2 Sucrose (export)