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CHAPTER 8 - Coggle Diagram
CHAPTER 8
Photosynthesis
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- 6CO2 + 12H2O + light energy → C6H12O6 + 6O2 + 6H2O
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2stages :
Light reactions: Use light energy,e in thylakoid membranes,Produce ATP, NADPH and O2
Calvin cycle: in the stroma, Uses ATP and NADPH to incorporate CO2 into carbohydrates, Energy storage,Requires massive input of energy ,Product is glyceraldehyde-3-phosphate (G3P)
Reactions That Harness:
Light Energy: electromagnetic radiation, waves,photons
Phase 1 – Carbon fixation:CO2 into RuBP using rubisco -Phase 2 – Reduction and carbohydrate production :ATP is used to convert 3PG into (1,3-BPG), NADPH electrons reduce it to (G3P),Only 2 G3P molecules used for carbohydrates Phase 3 Regeneration of RuBP :10 G3P are converted into 6 RuBP using 6 ATP
Environmental conditions: Light intensity, Temperature,Water availability
Trophic levels
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Photoautotroph: Use light as a source of energy. Green plants, algae, cyanobacteria
Heterotroph : Bacteria, protists, fungi, and animals
Chloroplast
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photosynthesis occurs internally
in leaves, in the mesophyll
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- Captured light energy to produce energy intermediate molecules, Thylakoid membranes of chloroplast contain :
Photosystem II: amazing redox machine nitial step,Excited electrons travel from PSII to PSI, Oxidizes water, generating O2 and H+, Releases energy
Two main components: Light-harvesting complex, which absorbs photons,Energy transferred- Reaction center, P680 → P680* , Water is oxidized , producing O2 gas
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Z scheme: Zigzag shape, Photosynthesis involves increases and decreases in the energy of an electron, a non-excited pigment molecule, starts with the lowest energy ,Photosystem I boosts the electron
Enhancement Effect : Simultaneous flashes,more than doubles the rate of photosynthesis -provided evidence for the existence of two photosystems
Photorespiration Decreases the Efficiency
of Photosynthesis: Rubisco functions as a carboxylase, Rubisco can also be an oxygenase, in hot and dry environments, CO2 low and O2 high
CAM plants :
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close their stomata during the day and open them at night,CO2 enters and is converted to malate ,Stomata close during the day to conserve water
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C4 Plants: Evolved a mechanism to minimize
photorespiration, making oxaloacetate in the first step of carbon fixation, Hatch-Slack pathway ,Leaves Mesophyll cells and Bundle-sheath cells