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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 o Factors: Formula = Photons (Light) + 3 ADP + 3 PO 4 + 2 NADP+ + 2H2O 3ATP + 2 NADPH + O2 + 2H+ Timeline: Photosystems II (p680; Chlorophyll A & B) Electron Transfer Chain/Proton Pumping Photosystem I (p700; Chlorophyll A) Formation of NADPH + Chemiosmosis of ATP Cyclic 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 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