BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor From PowerPoint ® Lectures for Biology: Concepts & Connections CHAPTER 7 Photosynthesis: Using Light to Make Food Modules 7.1 – 7.5
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Light - central to the life of a plant Photosynthesis is the most important chemical process on Earth –provides food for virtually all organisms Convert light energy -> chemical energy (sugar) Life in the Sun
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Photosynthesis - autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water AN OVERVIEW OF PHOTOSYNTHESIS Carbon dioxide WaterGlucoseOxygen gas PHOTOSYNTHESIS
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Plants, some protists, and some bacteria are photosynthetic autotrophs –They are the ultimate producers of food consumed by virtually all organisms 7.1 Autotrophs are the producers of the biosphere
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In aquatic environments, algae and photosynthetic bacteria are the main food producers Figure 7.1CFigure 7.1D
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings photosynthesis occurs primarily in the leaves, in the chloroplasts chloroplast: –stroma, a fluid –grana, stacks of thylakoids thylakoids contain chlorophyll –Chlorophyll - green pigment that captures light for photosynthesis 7.2 Photosynthesis occurs in chloroplasts
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The location and structure of chloroplasts Figure 7.2 LEAF CROSS SECTION MESOPHYLL CELL LEAF Chloroplast Mesophyll CHLOROPLAST Intermembrane space Outer membrane Inner membrane Thylakoid compartment Thylakoid Stroma Granum StromaGrana
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The O 2 liberated by photosynthesis is made from the oxygen in water 7.3 Plants produce O 2 gas by splitting water Figure 7.3A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Water molecules are split apart and electrons and H + ions are removed, leaving O 2 gas –These electrons and H + ions are transferred to CO 2, producing sugar 7.4 Photosynthesis is a redox process, as is cellular respiration Figure 7.4A Figure 7.4B Reduction Oxidation Reduction
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2 Reactions: –the light reactions and the Calvin cycle light reactions - convert light energy to chemical energy and produce O 2 Calvin cycle - makes sugar molecules from CO 2 using the energy-carrying products of the light reactions 7.5 Overview: Photosynthesis occurs in two stages linked by ATP and NADPH
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings An overview of photosynthesis Figure 7.5 Light Chloroplast LIGHT REACTIONS (in grana) CALVIN CYCLE (in stroma) Electrons H2OH2O O2O2 CO 2 NADP + ADP + P Sugar ATP NADPH
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Certain wavelengths of visible light drive the light reactions of photosynthesis 7.6 Visible radiation drives the light reactions THE LIGHT REACTIONS: CONVERTING SOLAR ENERGY TO CHEMICAL ENERGY Gamma rays X-raysUVInfrared Micro- waves Radio waves Visible light Wavelength (nm) Figure 7.6A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.6B Light Chloroplast Reflected light Absorbed light Transmitted light
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Each of the many light-harvesting photosystems consists of: –Chlorophyll that absorbs light energy and passes electrons 7.7 Photosystems capture solar power
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.7C Primary electron acceptor Photon Reaction center PHOTOSYSTEM Pigment molecules of antenna
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.7B Excitation of chlorophyll in a chloroplast Primary electron acceptor Other compounds Chlorophyll molecule Photon
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Two photosystems absorb light and transfer energy to chlorophyll electrons excited electrons passed down chain of photosystems to NADP Passing electrons make ATP and NADPH Water provide electrons and release Oxygen 7.8 In the light reactions, electron transport chains generate ATP, NADPH, and O 2
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Photosystem II regains electrons by splitting water, leaving O 2 gas as a by-product Figure 7.8 Primary electron acceptor Electron transport chain Electron transport Photons PHOTOSYSTEM I PHOTOSYSTEM II Energy for synthesis of by chemiosmosis
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Passing of electrons pump H + from stroma into thylakoid –flow of H + back through the membrane into stroma make ATP –In the stroma, the H + ions combine with NADP + to form NADPH 7.9 Chemiosmosis powers ATP synthesis in the light reactions
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The production of ATP by chemiosmosis in photosynthesis Figure 7.9 Thylakoid compartment (high H + ) Thylakoid membrane Stroma (low H + ) Light Antenna molecules Light ELECTRON TRANSPORT CHAIN PHOTOSYSTEM IIPHOTOSYSTEM IATP SYNTHASE
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Calvin cycle occurs in the chloroplast’s stroma –carbon fixation takes place and sugar is manufactured 7.10 ATP and NADPH power sugar synthesis in the Calvin cycle THE CALVIN CYCLE: CONVERTING CO 2 TO SUGARS INPUT Figure 7.10A OUTPUT: CALVIN CYCLE
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The Calvin cycle constructs G3P using –carbon from atmospheric CO 2 –electrons and H + from NADPH –energy from ATP Energy-rich sugar is then converted into glucose
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.10B Details of the Calvin cycle INPUT: Step Carbon fixation. In a reaction catalyzed by rubisco, 3 molecules of CO 2 are fixed. 1 1 Step Energy consumption and redox. 2 3P P P6 6 2 ATP 6 ADP +P 6 NADPH 6 NADP + 6P G3P Step Release of one molecule of G3P. 3 CALVIN CYCLE 3 OUTPUT: 1P Glucose and other compounds G3P Step Regeneration of RuBP. 4 G3P 4 3 ADP 3ATP 3 CO 2 5P RuBP3-PGA
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A summary of the chemical processes of photo- synthesis 7.11 Review: Photosynthesis uses light energy to make food molecules PHOTOSYNTHESIS REVIEWED AND EXTENDED Figure 7.11 Light Chloroplast Photosystem II Electron transport chains Photosystem I CALVIN CYCLE Stroma Electrons LIGHT REACTIONSCALVIN CYCLE Cellular respiration Cellulose Starch Other organic compounds