Photosynthesis: Capturing Energy
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Transcript of Photosynthesis: Capturing Energy
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
Copyright © 2005 Brooks/Cole — Thomson Learning
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
Copyright © 2005 Brooks/Cole — Thomson Learning
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
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
Calvin cycle
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
Summary of photosynthesis
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
C3 and C4 plant structure compared
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 8 Photosynthesis: Capturing Energy
Summaryof the C4
pathway