Photosynthesis Chapter 08 - 2024 (1) PDF

Chapter 8 Photosynthesis p.169 - 188 © 2017 Cengage Learning. All Rights  Lecture 11 Photosynthesis: light dependent reactions At the end of this section, you should be able to:  Describe chloroplast structure and function  Describe the relationship be...

Chapter 8 Photosynthesis p.169 - 188 © 2017 Cengage Learning. All Rights  Lecture 11 Photosynthesis: light dependent reactions At the end of this section, you should be able to:  Describe chloroplast structure and function  Describe the relationship between photons and chlorophyll  Explain how electron transport chain in the chloroplast uses energy to produce ATP and NADPH molecules  Explain where the different reactions take place  Differentiate photosystem II from photosystem I and describe their functions  Describe why oxygen is a by-product of photosynthesis  Distinguish between non-cyclic and cyclic electron transport  Explain how ATP is generated through a proton gradient (chemiosmosis) © 2017 Cengage Learning. All Rights Why It Matters? The most important process on earth Photosynthesis - the conversion of light energy to chemical energy in the form of sugar and other organic molecules Which organisms? Plants, some protists, green algae and bacteria Oxygen is a by-product of photosynthesis © 2017 Cengage Learning. All Rights 8.1 Photosynthesis: An Overview Autotrophs (autos = self; trophos = feeding) Organisms that use chemical energy to convert simple inorganic molecules to organic molecules Photoautotrophs Autotrophs use light (photo = light) as the energy source to convert CO2 into organic molecules (e.g. sugars) through photosynthesis (plants = primary producers) Organic molecules (biomass) energy for plants (through cellular respiration) food for consumers (heterotrophs) p.169 p.168 © 2017 Cengage Learning. All Rights 8.1 Photosynthesis: An Overview Heterotrophs (hetero = different; trophos = feeding) Consumers and decomposers, which need a source of energy from organic molecules to survive Source is the primary producers Food chain depends on photosynthesis, hence “photosynthesis is life” p.168 © 2017 Cengage Learning. All Rights Photosynthesis Photosynthesis uses sunlight, water, and CO2 to produce almost all organic matter on Earth, and supplies our atmosphere with oxygen The major product of photosynthesis is organic glucose (C6H12O6) 6 CO2 + 12 H2O → light → C6H12O6 + 6 O2 + 6 H2O p.168 © 2017 Cengage Learning. All Rights Photosynthesis overview Two stages: light-dependent and light-independent Light converted to ATP + NADPH (source of electrons and H+ is water) 6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2O Interlinked p.168 © 2017 Cengage Learning. All Rights Photosynthesis Overview Stomata Sunlight Sunlight Chloroplast Chloroplast and and NADP NADP H H Light- Light- Light- Light- dependent dependent independen independen reactions reactions tt(Stroma) reactions reactions ADP ADP + + and and NADP NADP ++ H H22O O (CH (CH22O) O) Organic nn Source of electrons molecules 2 H2O → 4 H+ + 4 e- + O2 6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2O P168 © 2017 Cengage Learning. All Rights Reactants & Products 6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2O Reactants:12 H2O 6 CO2 Products: 6 O2 C6H12O6 6 H2O p.168 © 2017 Cengage Learning. All Rights Two Stages in Photosynthesis Light-dependent reactions Energy of sunlight is absorbed and converted into chemical energy (ATP and NADPH) NADPH carries electrons that are pushed to high energy levels by absorbed light Electron transport chain © 2017 Cengage Learning. All Rights Where Reactions Take Place - Chloroplasts Shutterstock.com javarman/ Sunlight Chloroplast Cutaway of a small section One of the from the leaf photosynthetic cells, with green and chloroplasts Leaf’s upper surface Photosynthetic cells Large central NADPH vacuole Light- Light- CO 2 dependent independent reactions reactions O2 Stomata (through which O2 and CO 2 are Nucleus exchanged with the atmosphere) ADP + and Cutaway view of a chloroplast NADP + Outer membrane Inner membrane H2O (CH2O)n Thylakoids Stroma (space light absorption around thylakoids) by chlorophylls light-independent 6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2O and carotenoids reactions electron transfer ATP synthesis by ATP synthase Granum p168 -169 Stromal Thylakoid Thylakoid lamella lumen membrane © 2017 Cengage Learning. All Rights Chloroplast Structure An intermembrane compartment lies between the outer membrane and the inner membrane The compartment formed by the inner membrane is filled with a fluid (stroma) = light-independent reactions (CO2 fixation) Within the stroma, thylakoid membranes form flattened, closed sacs (thylakoids) enclosing the thylakoid lumen = light dependent reactions Grana p.169 © 2017 Cengage Learning. All Rights 8.2 The Light-Dependent Reactions of Photosynthesis Light-dependent reactions (light reactions) convert light energy to chemical energy Light reactions involve two main processes Light absorption (energy) Synthesis of NADPH and ATP Which light on the electromagnetic spectrum is absorbed? p.170 © 2017 Cengage Learning. All Rights The Electromagnetic Spectrum Electromagnetic spectrum Forms of radiant energy that differ in wavelength From radio waves (10 m) to gamma rays (10-6 nm) A. Range of the electromagnetic spectrum The shortest, Range of most Range of heat The longest, most energetic radiation reaching the escaping from the lowest-energy wavelengths surface of the Earth surface of the Earth wavelengths Gamma X-rays Ultraviolet Near-infrared Infrared Microwave Radio rays radiation radiation radiation s waves Visible light 400 45 500 550 600 65 70 0 0 0 Wavelength of visible light (nm) p.170 © 2017 Cengage Learning. All Rights Visible light or white light ????? A. Range of the electromagnetic spectrum The shortest, Range of most Range of heat The longest, most energetic radiation reaching the escaping from the lowest-energy wavelengths surface of the Earth surface of the Earth wavelengths Gamma X-rays Ultraviolet Near-infrared Infrared Microwave Radio rays radiation radiation radiation s waves Visible light 400 45 500 550 600 65 70 0 0 0 Wavelength of visible light (nm) Visible light has wavelengths between about 700 nm (red light) and 400 nm (blue light) The entire spectrum combined together as white light Energy in a unit of light (photon) is inversely proportional to wavelength The shorter the wavelength, the greater the energy of the photon p.170 © 2017 Cengage Learning. All Rights Photosynthetic Pigments In photosynthesis, light is A. Chlorophyll structure B. Carotenoid structure absorbed by green CH3 in chlorophyll a CHO in chlorophyll b pigments (chlorophyll a & b) X Light-absorbing region and yellow-orange pigments region Light-absorbing (carotenoids) Chlorophylls are the main photosynthesis pigments Hydrophobic side chain p.171 - 173 © 2017 Cengage Learning. All Rights Pigments and Electron Energy 1. When not absorbing light, electrons in a pigment molecule are at a relatively low energy level (ground state) 2. When an electron in a pigment absorbs the energy of a photon, it jumps to a higher energy level (excited state) 1. Electron at ground state Low energy level 2. Electron at exited state High energy level p.172 © 2017 Cengage Learning. All Rights  Effects of Light Absorbed by a Pigment 1. The excited electron returns to its ground state, releasing energy as heat or light (fluorescence) Electron at ground state Low energy level 2. The excited electron is Electron at excited state High energy level transferred from the pigment molecule to a nearby Either Or Or electron-accepting molecule (primary acceptor) 3. The energy of the excited electron is transferred to a neighboring pigment molecule, and the first Electron- Pigment accepting molecule molecule molecule returns to its 1 2 3 ground state p.172 © 2017 Cengage Learning. All Rights Light Receptor Pigments Chlorophylls (a & b) = major photosynthetic pigments in plants, green algae, and cyanobacteria Carotenoids = accessory pigments Chlorophylls and carotenoids = bound to proteins embedded in photosynthetic membranes In plants and green algae, they are located in the thylakoid membranes of chloroplasts p.172 © 2017 Cengage Learning. All Rights Chlorophyll a and Accessory Pigments Specialized chlorophyll a molecules (reaction centres) pass excited electrons to primary acceptors, and are directly involved in transforming light into chemical energy Other chlorophyll molecules and carotenoids act as accessory pigments that pass their energy to the specialized chlorophyll a molecules p.171-172 © 2017 Cengage Learning. All Rights 8.2 …The Light-Dependent Reactions of Photosynthesis Light-dependent reactions (light reactions) convert light energy to chemical energy Light reactions involve two main processes: Light absorption Synthesis of NADPH and ATP p.172 © 2017 Cengage Learning. All Rights Photosystems Light-absorbing pigments are organized with proteins and other molecules into large complexes (photosystems II & I) embedded in thylakoid membranes and stromal lamellae Photosystems are the sites at which light energy is converted into chemical energy 2 types Photosystem II and photosystem I carry out different parts of the light-dependent reactions p.172-174 © 2017 Cengage Learning. All Rights A Photosystem Photosystem consists of an Light O2 ATP CO2 antenna complex (light-harvesting Light reactions NADPH Calvin cycle complex) and a reaction center Thylakoid membrane ADP NADP+ H2 O (CH2O)n The antenna complex contains Stroma Photosystem many chlorophyll pigments Antenna complex: aggregate of chlorophyll and carotenoid pigments Reaction center (anchored to specific membrane Photon of light Primary electron acceptor proteins) to optimize the capture of light energy e– Electron is e– passed to the electron transfer system Transfer of Special subsets Pigment energy of chlorophyll a molecules molecules (two are shown) Thylakoid lumen p.172-174 © 2017 Cengage Learning. All Rights P700 and P680 The reaction center of photosystem I contains a pair of specialized chlorophyll a molecules (P700) = absorbs light optimally at 700 nm The reaction center of photosystem II contains a pair of specialized chlorophyll a molecules (P680) = absorbs PS II PS I light optimally at 680 nm P680 P700 p.172-174 © 2017 Cengage Learning. All Rights Linear Electron Flow - Z scheme (non-cylic e- transport) Light Thylakoid ADP membrane NADP+ Photosystem I Primary acceptor Ferredoxin Photosystem II Cytochrome complex Primary acceptor NADP+ Light + Plasto- energy quinone pool Light energy Energy level of P700 electrons Plastocyanin P680 ATP synthase To light-independent ADP + reactions ATP p.174 -175 (Calvin cycle) H+ from H2O and electron transfer creates a gradient for ATP synthesis. © 2017 Cengage Learning. All Rights Linear Electron Flow - Z scheme 1. Chlorophyll of the antenna complex absorb photons PS I 2. Absorbed light energy Cytochrome 3 4 PS II complex reaches P700 & P680 (reaction center) by 3 NADP+ PQ 1 + inductive resonance 1 4 3. Excited electrons (2e-) Energy level of PC electrons passed to primary 2 acceptor, P700 4. then to the electron 2 transfer chain (ETC) P680 ADP + To light- ATP independent system, which carries reactions (Calvin cycle) electrons from PSII & PSI p.174-176 © 2017 Cengage Learning. All Rights Linear Electron Flow - Z scheme The electron transfer system consists of the mobile electron PS I carrier plastoquinone (PQ), a Cytochrome cytochrome complex, and the PS II complex mobile carrier plastocyanin (PC), NADP+ connecting PSII & PSI PQ + Energy level of “High energy electrons” pass PC electrons through PSII, the electron transfer system & PSI as the series of electron carriers are alternately reduced and ADP + ATP To light- independent oxidized reactions (Calvin cycle) p.174 -176 © 2017 Cengage Learning. All Rights Linear Electron Flow - Why is called Z scheme? 1. Electrons from “splitting” of water flow through PS II, PS I becoming excited to a higher energy level through absorbed 4 Cytochrome light energy in P680 PS II complex 2. The electrons flow “downhill” in NADP+ + energy level PQ 2 (oxidation/reduction) through 3 Energy level of electron transfer chain (ETC) PC electrons 3. When electrons move through PS I, they are excited a “second” time through 1 absorbed light energy in P700 ADP + ATP To light- independent 4. Electrons flow “downhill” to reactions (Calvin cycle) NADP reductase - NADPH p.174 -176 © 2017 Cengage Learning. All Rights Linear Electron Flow - Z scheme The electron transfer system consists of the mobile electron PS I carrier plastoquinone (PQ), a cytochrome complex, and the Cytochrome mobile carrier plastocyanin (PC), PS II complex linking PSII & PSI NADP+ + As electrons pass through the PQ 2 system, they release free energy 3 Energy level of at each transfer from a donor to PC electrons an acceptor molecule Some of this free energy is used to create a gradient of H+ across 1 the membrane, which provides ADP + ATP To light- independent energy for ATP synthesis reactions (Calvin cycle) (chemiosmosis) p.174 -176 © 2017 Cengage Learning. All Rights Linear Electron Flow - Z scheme NB: Electrons obtained from the “splitting of water” are used to PS I synthesize NADPH and ATP NADPH synthesis: Cytochrome 1 2 PS II complex 1. High-energy electrons from NADP+ PSI enter a short electron PQ + transfer system, leading to the final acceptor NADP+ Energy level of PC electrons 2. NADP+ reductase reduces NADP+ to NADPH, using 2 electrons and 2 protons This = linear electron flow To light- ADP + ATP (non-cyclic) because independent reactions (Calvin cycle) electrons travel one-way from H2O to NADP+ p.174 -176 © 2017 Cengage Learning. All Rights Linear Electron Flow - Z scheme NB: Electrons obtained from the “splitting of water” are used to PS I synthesize NADPH and ATP Cytochrome PS II complex ATP synthesis: 1. As electrons pass through the NADP+ + PQ system, they release free 1 energy at each transfer from a Energy level of PC donor to an acceptor molecule electrons 2. Some of this free energy is used to create a “gradient of 2 H+” across the membrane, To light- this provides energy for ATP ADP + ATP independent synthesis (chemiosmosis) reactions (Calvin cycle) p.174 -176 © 2017 Cengage Learning. All Rights  Electron transfer ( Z scheme ) & Chemi-osmosis Strom Electron transfer system Chemiosmosis a To light- independent reactions Photosystem II Cytochrome Photosystem I Low H+ (Calvin cycle) complex Light Primary acceptor Light Antenna energy energy complex Ferredoxin NADP+ Pigment molecules Plastoquinone Stator Water-splitting Plastocyanin complex ATP synthase High H+ Chemi-osmosis Thylakoid Thylakoid lumen membrane p.176 © 2017 Cengage Learning. All Rights Energy Yield Strom Electron transfer system Chemiosmosis a To light- Photosystem II Cytochrome Photosystem I Low H+ independent Light Antenna reactions complex energy complex Ferredoxin NADP+ (Calvin cycle) Primary acceptor Light energy Pigment molecules Plastoquinone Stato Water-splitting Plastocyanin r complex ATP synthase High H+ Thylakoid Thylakoid lumen membrane The overall yield of the noncyclic electron flow pathway is 1 NADPH and 1 ATP for each “pair of electrons” produced from the splitting of 1 H2O molecule Photophosphorylation (ATP production) Synthesis of ATP coupled to the transfer of electrons energized by photons of light Proton-motive force (H+ gradient) contributes energy for ATP synthesis by ATP synthase (chemi-osmosis) p.175 -176 © 2017 Cengage Learning. All Rights Energy Yield Strom Electron transfer system Chemiosmosis a To light- Photosystem II Cytochrome Photosystem I Low H+ independent Light Antenna reactions complex energy complex Ferredoxin NADP+ (Calvin cycle) Primary acceptor Light energy Pigment molecules Plastoquinone Stato Water-splitting Plastocyanin r complex ATP synthase High H+ Thylakoid Thylakoid lumen membrane The overall yield of the noncyclic electron flow pathway is 1 NADPH and 1 ATP for each “pair of electrons” produced from the splitting of 1 H2O molecule Photophosphorylation (ATP production) Synthesis of ATP coupled to the transfer of electrons energized by photons of light Proton-motive force (H+ gradient) contributes energy for ATP synthesis by ATP synthase (chemi-osmosis) p.175 -176 NB: Non-cyclic photophosphorylation © 2017 Cengage Learning. All Rights Cyclic Electron Flow (provides additional ATP) In some cases, photosystem I works Lig ht independently of photosystem II, in a circular Thylakoid ADP NAD Photosystem membran I process (cyclic electron P+ e Ferredoxin flow) Cytochrome complex NADP+ reductas Electrons flow from PS I to e NAD Ferredoxin ferredoxin, then back to Plasto- P+ quinone pool P700 through the cytochrome complex – does not produce NADPH Plastocyanin + H+ With each cycle, more H+ is ATP synthase pumped across the To light- ADP independent + reactions thylakoid membranes – H+ from electron H 2O and (Calvin cycle) transfer creates a gradient for driving ATP synthesis p.177 ATP synthesis. © 2017 Cengage Learning. All Rights NB: Cyclic e transport does not involve PSII, only PSI Does not evolve Oxygen Does not form NADPH Only contributes to H+ gradient for ATP synthesis Important under stress conditions (avoid NADPH formation, a reducing agent for ROS, to avoid oxidative damage) 2NADPH and 3ATP molecules are required for the next phase= The light independent reactions (CO2 fixation/Calvin cycle) © 2017 Cengage Learning. All Rights Lecture 12 At the end of this section, you should be able to:  Explain where the Calvin cycle takes place  Discuss the Calvin cycle (three phases)  Explain the important role of the Calvin cycle  Explain the contribution and role of photorespiration © 2017 Cengage Learning. All Rights 8.3 The Light-Independent Reactions of Photosynthesis Occurs in stroma of chloroplast CO2 fixation takes place in the light-independent reactions of photosynthesis (Calvin cycle) Rubisco (one molecule Electrons (e-) carried by per cycle) Ribulose RuBP 1,5-bisphosphate (RuBP) 3-Phospho- NADPH provide reducing carboxylase/ glycerate (3PGA) oxygenase (rubisco) power to fix CO2 into Ribulose 5-phosphate kinase Phase l Carbon fixation 3-Phospho- glycerate kinase carbohydrates (sugars) Calvin cycle 1,3-Bisphospho- glycerate and other organic Phase 3 Phase Ribulose Regenerati 2 5-phosphate on Reductio n l,3-Bisphospho- molecules glycerate kinase ATP supplies additional Glyceraldehyde- 3- phosphate (G3P) energy 3 steps: carbon fixation, p.178 To reactions synthesizing reduction, regeneration sugars and other organic © 2017 Cengage Learning. All Rights compounds Three Phases of the Calvin Cycle 1: Carbon fixation CO2 (through stomata) is added to ribulose 1,5- bisphosphate (RuBP) A transient 6C molecule is (one molecule per cycle) Rubisco cleaved to two 3C molecules Ribulose 1,5-bisphosphate (RuBP) RuBP carboxylase/ 3-Phospho- glycerate (3PGA) - 3-phosphoglycerate oxygenase (rubisco) (3PGA) 1 Ribulose 5-phosphate kinase Phase l Carbon fixation 3-Phospho- glycerate kinase Calvin Enzyme: RuBP cycle 1,3-Bisphospho- glycerate Phase 3 Phase Ribulose Regenerati 2 5-phosphate on Reductio carboxylase/oxygenase n l,3-Bisphospho- glycerate kinase (rubisco) Glyceraldehyde- 3- phosphate (G3P) Plants that initially fix carbon in this way = C3 plants To reactions synthesizing sugars and other organic compounds p.178-181 © 2017 Cengage Learning. All Rights Three Phases of the Calvin Cycle (cont’d.) 2: Reduction A phosphate group (P) from ATP and electrons (e-) from NADPH reduces 3PGA to Glyceraldehyde-3-phosphate (G3P) (one molecule Rubisco per cycle) Enzymes: 3-phospho glycerate kinase & Ribulose 1,3 bisphosphoglycerate dehydrogenase RuBP 1,5-bisphosphate (RuBP) 3-Phospho- carboxylase/ glycerate (3PGA) oxygenase (rubisco) One G3P exits the cycle – 3-Phospho- Ribulose Phase l glycerate 5-phosphate Carbon fixation kinase kinase Calvin used to build six-carbon cycle 1,3-Bisphospho- glycerate glucose and other organic 2 Phase 3 Phase Ribulose Regenerati 2 5-phosphate on Reductio n l,3-Bisphospho- molecules glycerate kinase Glyceraldehyde- 3- Other G3P are used to phosphate (G3P) regenerate RuBP To reactions p.178-181 synthesizing sugars and other organic compounds © 2017 Cengage Learning. All Rights Three Phases of the Calvin Cycle (cont’d.) 3: Regeneration G3P enters a series of reactions that yields the five- carbon sugar - ribulose 5-phosphate Rubisco (one molecule In the final reaction of the per cycle) Ribulose RuBP 1,5-bisphosphate (RuBP) 3-Phospho- cycle, a phosphate group carboxylase/ glycerate (3PGA) oxygenase (rubisco) (P) is transferred from Ribulose 5-phosphate kinase Phase l Carbon fixation 3-Phospho- glycerate kinase ATP to regenerate the Calvin cycle 1,3-Bisphospho- ribulose 1,5- glycerate 3 Phase 3 Phase Ribulose Regenerati 2 5-phosphate on Reductio bisphosphate (RuBP) n l,3-Bisphospho- glycerate kinase used in the first reaction Glyceraldehyde- 3- phosphate (G3P) Enzyme: Ribulose 5-phosphate kinase To reactions synthesizing sugars and other p.178-181 organic compounds © 2017 Cengage Learning. All Rights Summary: The Calvin Cycle For each turn of the cycle, 2 ATP and 2 NADPH are used in the reduction phase, and another Rubisco ATP is used in regeneration (one molecule per cycle) phase, for a total of 3 ATP and 2 Ribulose RuBP 1,5-bisphosphate (RuBP) 3-Phospho- carboxylase/ glycerate (3PGA) oxygenase (rubisco) NADPH Ribulose 5-phosphate Phase l 3-Phospho- glycerate One complete turn of the cycle Carbon fixation kinase kinase Calvin cycle includes: 1,3-Bisphospho- glycerate Phase 3 Phase Ribulose Regenerati 2 5-phosphate on Reductio n l,3-Bisphospho- glycerate kinase CO2 + 2 NADPH + 3 ATP → Glyceraldehyde- 3- phosphate (G3P) (CH2O) + 2 NADP+ + 3 ADP + 3 Pi To reactions synthesizing sugars and other organic compounds © 2017 Cengage Learning. All Rights Summary: The Calvin Cycle It takes three turns to produce one net G3P G3P is the primary building Rubisco (one molecule block for producing glucose per cycle) Ribulose and many other organic RuBP 1,5-bisphosphate (RuBP) 3-Phospho- carboxylase/ glycerate (3PGA) oxygenase (rubisco) molecules Ribulose 5-phosphate Phase l Carbon fixation 3-Phospho- glycerate kinase It takes six turns of the kinase Calvin cycle 1,3-Bisphospho- cycle to produce enough glycerate Phase 3 Phase Ribulose Regenerati 2 5-phosphate on Reductio n (CH2O) units to make the l,3-Bisphospho- glycerate kinase six-carbon carbohydrate Glyceraldehyde- 3- glucose phosphate (G3P) To reactions synthesizing sugars and other G3P organic compounds p.180 © 2017 Cengage Learning. All Rights Oxygen and Earth’s Atmosphere Oxygen released by the water-splitting reaction of photosynthesis profoundly changed Earth’s atmosphere Allowed for aerobic respiration, in which oxygen serves as the final electron acceptor in cellular oxidations The existence of all animals depends on oxygen provided by the water-splitting reaction of photosynthesis © 2017 Cengage Learning. All Rights  8.4 Photorespiration- an alternative to Carbon Fixation-C3 Plants RuBP Carboxylase/Oxygenase (Rubisco) A Carboxylation reaction of Rubisco Rubisco RuBP (5C) + CO2 2 x 3-phosphoglycerate (3PGA; 3C) Photosynthesis (C3) B Oxygenation reaction of Rubisco Rubisco RuBP (5C) + O2 1 3PGA (3C) + 1 Phosphoglycolate (2C) Toxic In C3 plants when its hot and dry (less CO2 available) NADPH & ATP from light phase required Photorespiration Photorespiration reduces photosynthesis efficiency= impairs To reactions plant growth releasing CO2 To overcome photorespiration, two alternative processes of carbon fixation - C4 & CAM photosynthesis p.181 © 2017 Cengage Learning. All Rights Photosynthesis and Cellular Respiration Overall reactions of Light Photosynthesis Cellular respiration photosynthesis and Photophosphorylation Direction of reactions Oxidative cellular respiration are phosphorylation Electron transfer system Electron transfer and chemiosmosis (light- system and chemiosmosis basically the reverse of dependent reactions) each other Electrons carried by NADH and FADH2 ATP, NADPH Mitochondrion Chloroplast Citric acid cycle Reactants of Calvin photosynthesis (CO2 cycle (light- independent reactions) Acetyl–CoA Pyruvate oxidation and H2O) are products G3P Pyruvate of cellular respiration, Cytosol Cytosol G3P and reactants of cellular Sugars and Glucose and other fuel molecules respiration (glucose and other organic Glycolysis molecules O2) are products of H2O, CO2 Reactants Glucose, O2 CO2, H2O O2, Sugars (Glucose) photosynthesis Products p.183-184 © 2017 Cengage Learning. All Rights Photosynthesis and Cellular Respiration Light Both have key Photosynthesis Cellular respiration Direction of Photophosphorylation reactions Oxidative phosphorylation phosphorylation Electron transfer system Electron transfer and chemiosmosis (light- system and dependent reactions) chemiosmosis reactions involving an electron transfer Electrons carried by NADH and FADH2 ATP, NADPH system, followed by Mitochondrion Chloroplast Citric acid cycle chemiosmotic synthesis of ATP Calvin cycle (light- Acetyl–CoA independent reactions) Pyruvate oxidation G3P G3P is found in the Pyruvate Cytosol Cytosol pathways of both G3P Glucose and other processes Sugars and fuel molecules other organic Glycolysis molecules H2O, CO2 Reactants Glucose, O2 p.183-184 O2, Sugars (Glucose) Products CO2, H2O © 2017 Cengage Learning. All Rights