Download Photosynthesis - Lecture Guide

Photosynthesis
Origin of Life’s Power: Sun  Phototrophs: Photosynthesis (Endergonic/Anabolic/Endothermic Reaction  Sugar All Phototrophs +
Heterotrophs: Cellular Respiration (Catabolic/Exothermic/Exergonic)  Energy for Life’s Anabolic Pathways
Cellular Respiration vs. Photosynthesis
Photosynthesis Reactants & Products
 Requires Carbon Dioxide and Water (Reactants)
 Yields Glucose and Oxygen Gas (Products)
ATP & Cellular Energy
Combustion vs. Oxidation-Reduction & Cellular Energetics
 Electrons & Potential
 Oxidation & Reduction of Electron-Carrier Intermediates (When charged is produced the uncharged is consumed; vice-versa)
o NADP+  NADPH
o ADP  ATP
 Actually based on 2 separate reactions: Light / Dark Reactions
o Light-Dependent (Photosystems)  Oxidation of Water to Oxygen (+H)
o Light-Independent: Calvin Cycle (Carbon Fixation)  Reduction of Carbon Dioxide (+H) to Glucose
Plant Leaves
 Stomata
 Guard Cells
 Vascular Cells
 Epithelial Cells
 Mesophyll Cells
Mesophyll Cells
 Solar Panels
 Only cells that can photosynthesize
Chloroplasts [Solar Cell: Light (Kinetic Energy)  Chemical (Potential Energy)]
 Living
 Endosymbiont
 Role of Lumen, Stroma, Grana, & Thylakoid Membranes
Pigments
 Chlorophyll A (Blue-Green)
 Absorption of solar energy based mainly on Magnesium molecule at the center of Chlorophyll pigments
 Accessory Pigments
o Chlorophyll B (Yellow-Green)
o Carotenoids (Orange)
o Xanthopyll (Yellow)
o Phycobilins
 Pheophytin A (Gray-Brown)
 Pheophytin B (Yellow-Brown)
o Others
 Lutein
 Zeaxanthin
 Lycopene
 The point of different pigments
Processes (All equations exclude uncharged carriers)
 Light Dependent
o Non-Cyclic:
 Important Facts:
 Happens in the thykaloid membranes
 Splits water (photolysis)
 Yields Oxygen Gas
 Involves electron transfer
 Involves formation and use of proton potential (Chemiosmosis)
 ADP & NADP+ (Electron Acceptors)  ATP & NADPH (Charged carries of energy to be used by Calvin
Cycle)
 Provides energy for dark reactions
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Factors:
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 Formula = Photons (Light) + 3 ADP + 3 PO 4 + 2 NADP+ + 2H2O  3ATP + 2 NADPH + O2 + 2H+
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Timeline:
Photosystems II (p680; Chlorophyll A & B)  Electron Transfer Chain/Proton Pumping  Photosystem I
(p700; Chlorophyll A)  Formation of NADPH + Chemiosmosis of ATP
Cyclic
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Important facts:
 Photosystem I only (p700; Chlorophyll A)
 No NADPH is produced  Cannot power Calvin Cycle
 No water required (no photolysis of water)
 No oxygen released
 Insufficient for long term survival of the plant
 Some bacteria perform only this cycle (anoxygenic photosynthesis)
 Timeline:
 Sunlight is absorbed by electrons inside Magnesium atoms on Photosystem I
 Excited electrons from Photosystem II are transferred to the ferredoxin (oxidation of Photosystem I and
reduction of FD)
 FD is oxidized as it transfers electrons to reduce PQ
 PQ is oxidized as it transfer electrons to reduce B6F
 Like in the non-cyclic ETC, the cytochrome B6F + PQ complex pumps protons from stroma to lumen
 A proton potential is formed in lumen
 Chemiosmosis / Photophosphorylation of ATP occurs as discussed above
 No water involved
 Electrons can be boosted in pairs in each cycle to pump two H+ from stroma to lumen each time the process
is completed, as opposed to eight in the cyclic.
 Process yields less net ATP (since no protons are introduced from photolysis of water)
Light-Independent: Carbon Fixation (Calvin Cycle)
1) CO2 Absorption via Rubisco  Unstable 6C molecule  2x PGA (3C)
2) Reduction of PGA  PGAL (G3P) by adding PO4 (From ATP) and H+ from (NADPH)
3) Regeneration of RuBP: 5G3P recycled to form 3RuBP [at the expense of 3ATP) and 1 out of 6 G3P exists cycle to
become building block for macromolecules
 One turn will make ½ of glucose molecule
 G3P can also be used as building block for protein/lipid monomers
Temperature / Humidity / Intensity of Light
Limiting Factors on Land / Water
Shut down of non-cyclic photosynthesis  Photorespiration
Stomata & water loss
Photosynthetic Adaptations
 C3
 C4
 CAM
Photosynthesis
 Role of Enzymes
 Mesophyll Cells vs. Whole Plant  Photosynthesis + Cellular Respiration in Plants
 Water Production
 Algae vs. Plants & Photosynthesis
 Importance for Diversity of Life on Earth
Key Information
 Role of Photosynthesis
 Reaction
 Oxidation-Reduction in Photosynthesis
 Cellular Respiration vs. Photosynthesis
 Leaf, Mesophyll Cell, & Chloroplast Structure
 Photosynthetic Pigments
 Light-Dependent vs. Light-Independent
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Sequence of Non-Cyclic
Chemiosmosis of ATP at Thylakoid Membrane (Similarities to Cellular Respiration ETC)
Cyclic vs. Non Cyclic Light-Reactions
Light-Independent Depends on Light-Dependent
Calvin Cycle Sequence
Where is Oxygen Produced / Water Consumed
Where is Carbon Fixated
Where is Glucose Produced
Where is ATP Produced / Consumed
Variations (C3; C4; CAM)
Photorespiration
Photosynthesis Research
Factors of Photosynthesis (Heat, Temperature, Light-Intensity; Humidity)
Role of Enzymes
Mesophyll Cells vs. Whole Plant  Photosynthesis + Cellular Respiration in Plants
Algae vs. Plants & Photosynthesis
Importance for Diversity of Life on Earth