photosynthesis: capturing energy
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Photosynthesis: Capturing Energy. Light Composed of photons Visible light small portion of electromagnetic spectrum All energy travels as waves Shorter wavelengths have more energy than longer wavelengths. Electromagnetic spectrum. Chloroplasts Organelles enclosed by a double membrane - PowerPoint PPT PresentationTRANSCRIPT
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition Solomon • Berg • Martin
Chapter 8
Photosynthesis: Photosynthesis: Capturing EnergyCapturing Energy
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
• Light• Composed of photons
• Visible light small portion of electromagnetic spectrum• All energy travels as waves• Shorter wavelengths have more
energy than longer wavelengths
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
Electromagneticspectrum
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
• Chloroplasts• Organelles enclosed by a double
membrane• Site of photosynthesis• Located mainly within mesophyll cells
inside leaf
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
Site of photosynthesis
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Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
• Chlorophyll• Main photosynthetic pigment• Chlorophyll a, chlorophyll b,
carotenoids, and other photosynthetic pigments are components of thylakoid membranes of chloroplasts
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
• Photosynthesis is redox process• Light energy captured and converted
to carbohydrates• Hydrogens from water reduce carbon• Oxygen derived from water becomes
oxidized
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
• Two phases of photosynthesis• Light-dependent
–In thylakoids–Electrons energized by light generate
ATP and NADPH
• Carbon fixation–In stroma–Compounds generated in phase one
provide energy for formation of carbohydrate
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
Overview of photosynthesis
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
• Photosystems I and II• Two types of photosynthetic units
involved in photosynthesis• Each photosystem includes
–Chlorophyll molecules–Multiple antenna complexes
• Photosystem I reaction center–P700 has absorption peak at 700 nm
• Photosystem II reaction center–P680 has absorption peak at 680 nm
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
Photosystem
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
• Noncyclic electron transport• ATP and NADPH formed • Electrons energized by absorption of
light and pass through electron transport chain to NADP+
• Series of redox reactions• Electrons given up by P680 are
replaced by electrons from photolysis of H2O
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
Noncyclic electron transport
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
• Cyclic electron transport• Electrons from photosystem I
returned to photosystem I• ATP produced by chemiosmosis• No NADPH or O2 generated
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
• ATP synthesis and electron transport• Electrons move down electron
transport chain• Protons (H+) move from stroma to
thylakoid lumen, creating proton gradient
• Greater concentration of H+ lowers the pH
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
Accumulation of protons in thylakoid lumen
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Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
Electron transport and chemiosmosis
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
• Carbon fixation• Energy of ATP and NADPH used in
formation of organic molecules from CO2
12 NADPH + 18 ATP + 6 CO2 →C6H12O6 + 12 NADP + + 18 ADP + 18 Pi + 6 H2O
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
• Three phases of Calvin cycle• CO2 uptake• Carbon reduction• RuBP regeneration
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Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
Calvin cycle
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Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
Summary of photosynthesis
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Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
C3 and C4 plant structure compared
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Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
Summaryof the C4
pathway