AP BIOLOGY CHAPTER 10
Figure 10.0 Sunbeams
Figure 10.1 Photoautotrophs
Figure 10.2 Focusing in on the location of photosynthesis in a plant
Photosynthesis
6CO2 + 6H2O -- > C6H12O6 + 6O2
• Seems like the reverse of respiration, but the steps
aren’t backwards!
• Occurs in green portions of plants, primarily
chloroplasts in leaves
• Anabolic process since molecules built up
• Redox reactions involved
• Oxygen released by splitting water (van Neil)
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AP BIOLOGY CHAPTER 10
Figure 10.3 Tracking atoms through photosynthesis
Figure 10.4 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle (Layer 3)
Figure 10.5 The electromagnetic spectrum
Reactions Overview
• Light reactions: cyclic and non-cyclic
photophosphorylation
• Dark reactions: Calvin cycle
• Light reactions use pigments (chlorophyll a, b,
carotenoids) to capture light. Pigments located
along thylakoid membranes, organized into
reaction centers
• P680 (photosystem II) and P700 (photosystem I)
absorb light best at 680 and 700 nm. The light is
in the visible part of electromagnetic spectrum.
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AP BIOLOGY CHAPTER 10
Figure 10.6 Why leaves are green: interaction of light with chloroplasts
Figure 10.7 Determining an absorption spectrum
Figure 10.8 Evidence that chloroplast pigments participate in photosynthesis: absorption and action spectra
for photosynthesis in an alga
Figure 10.9 Location and structure of chlorophyll molecules in plants
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AP BIOLOGY CHAPTER 10
Figure 10.09x Chlorophyll
Figure 10.10 Excitation of isolated chlorophyll by light
Figure 10.11 How a photosystem harvests light
Reactions Overview
• Photosystems create ATP through
photophosphorylation.
• Noncyclic: PS2 generates ATP, PS1 generates
NADPH, water split by sunlight (photolysis)
• Cyclic: PS1 generates ATP, no NADPH, no split
of water
• Both reactions occur in thylakoids
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AP BIOLOGY CHAPTER 10
Figure 10.12 How noncyclic electron flow during the light reactions generates ATP and NADPH (Layer 5)
Figure 10.13 A mechanical analogy for the light reactions
Figure 10.14 Cyclic electron flow
Figure 10.16 The light reactions and chemiosmosis: the organization of the thylakoid membrane
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AP BIOLOGY CHAPTER 10
Figure 10.15 Comparison of chemiosmosis in mitochondria and chloroplasts
Calvin Cycle
• Products of light rxn are used to make sugar
• CO2 source of carbon
• CO2 turned into carbs through carbon fixation
• Also called the C3 pathway
Figure 10.17 The Calvin cycle (Layer 3)
Special Considerations
• Photorespiration is a relic of earlier times when
CO2 was more prevalend, O2 less.
• O2 enters Calvin cycle instead of CO2
• No ATP produced
• Fostered in hot, dry conditions
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AP BIOLOGY CHAPTER 10
Figure 10.18 C4 leaf anatomy and the C4 pathway
C4 and CAM
• C4 plants use an alternate form of Calvin cycle
• PEP carboxylase accepts CO2, not rubisco
• Bundle sheath and mesophyll cells separate initial
carbon fixation from the cycle itself
• CAM plants function well in hot, arid conditions.
• Stomata open at night, close during day.
• Light reactions during day, Calvin cycle at night.
Figure 10.19 C4 and CAM photosynthesis compared
Figure 10.20 A review of photosynthesis
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