Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Lectures by Chris C. Romero PowerPoint ® Lectures for Essential Biology, Third Edition – Neil Campbell, Jane Reece, and Eric Simon Essential Biology with Physiology, Second Edition – Neil Campbell, Jane Reece, and Eric Simon CHAPTER 7 Photosynthesis: Using Light to Make Food
Biology and Society: Plant Power for Power Plants On a global scale the productivity of photosynthesis is astounding. All of the food consumed by humans can be traced back to photosynthetic plants. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings An “energy plantation” –Is a renewable energy source.
Figure 7.1
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Basics of Photosynthesis Almost all plants are photosynthetic autotrophs, as are some bacteria and protists. –They generate their own organic matter through photosynthesis. Cyanobacteria (Oscillatoria)
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Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Chloroplasts: Sites of Photosynthesis Photosynthesis –Occurs in chloroplasts.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Chloroplasts –Are found in the interior cells of leaves. –Contain stroma, a thick fluid. –Contain thylakoids, membranous sacs.
Figure 7.3
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Overall Equation for Photosynthesis The reactants and products of the reaction
Unnumbered Figure 7.1
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings In photosynthesis, –Energized electrons are added to carbon dioxide to make sugar. –Sunlight provides the energy.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings A Photosynthesis Road Map Photosynthesis is composed of two processes: –The light reactions convert solar energy to chemical energy. –The Calvin cycle makes sugar from carbon dioxide.
Figure 7.4
The Light Reactions: Converting Solar Energy to Chemical Energy Chloroplasts are chemical factories powered by the sun –That convert solar energy into chemical energy. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Nature of Sunlight Sunlight is a type of energy called radiation –Or electromagnetic energy. The full range of radiation is called the electro- magnetic spectrum.
Figure 7.5
The Process of Science: What Colors of Light Drive Photosynthesis? In 1883, German biologist Theodor Engelmann –Performed an experiment using bacteria and algae and determined that certain types of light drive photosynthesis. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
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Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Chloroplasts absorb select wavelengths of light that drive photosynthesis. Light and Pigments
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Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Chloroplast Pigments Chloroplasts contain several pigments: –Chlorophyll a –Chlorophyll b –Carotenoids
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Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings How Photosystems Harvest Light Energy Light behaves as photons, discrete packets of energy.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Chlorophyll molecules absorb photons. –Electrons in the pigment gain energy. –The energy is released and used.
Figure 7.9
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings A photosystem –Is an organized group of chlorophyll and other molecules. –Is a light-gathering antenna.
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Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings How the Light Reactions Generate ATP and NADPH The light reactions of photosynthesis
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Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Two types of photosystems cooperate in the light reactions.
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Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings An electron transport chain –Connects the two photosystems. –Releases energy that the chloroplast uses to make ATP.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The light reactions in the thylakoid membrane Light Reactions
Figure 7.13
The Calvin Cycle: Making Sugar from Carbon Dioxide The Calvin cycle –Functions like a sugar factory within a chloroplast. –Regenerates the starting material with each turn. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings Calvin Cycle
Figure 7.14
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Water-Saving Adaptations of C 4 and CAM Plants C 3 plants –Use CO 2 directly from the air. –Are very common and widely distributed.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings C 4 plants –Close their stomata to save water during hot and dry weather. –Can still carry out photosynthesis. CAM plants –Open their stomata only at night to conserve water.
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Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Environmental Impact of Photosynthesis A review of photosynthesis
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Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Photosynthesis has an enormous impact on the atmosphere. –It swaps O 2 for CO 2.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings How Photosynthesis Moderates Global Warming Greenhouses used to grow plant indoors –Trap sunlight that warms the air inside.
Figure 7.17
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings A similar process, the greenhouse effect, –Warms the atmosphere. –Is caused by atmospheric CO 2.
Figure 7.18
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Greenhouse gases are the most likely cause of global warming, a slow but steady rise in the Earth’s surface temperature. –Destruction of forests may be increasing this effect.
Evolution Connection: The Oxygen Revolution The atmospheric oxygen we breathe is a by- product of photosynthesis. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Cyanobacteria were the first organisms to carry out photosynthesis. The production of oxygen changed the Earth forever. –The “oxygen revolution” was a major episode in the history of life on Earth.
Figure 7.19