Photosynthesis PDF

Booster Prep Booster Cheat Sheets™– Photosynthesis ©©...

Booster Prep Booster Cheat Sheets™– Photosynthesis ©© Copyright Copyright2022, 2024,Booster BoosterPrep AllAllRights Prep Inc. Rights Reserved. Reserved. Overview Chloroplast Anatomy Photosynthesis: Light energy from the sun is used to synthesize glucose. Photosynthesis takes place in chloroplast, a double-membraned organelle in plant cells. 4 3 Chlorophyll A, B, and carotenoids absorb energy from sunlight 1. 1 Outer Membrane 5 Photons excite electrons 2. 2 Granum – Stacks of thylakoids 6 2 Excited electrons are unstable and re-emit energy 3. 3 Thylakoid Energy absorbed by Chlorophyll A molecules, P680 (PSII) & P700 (PSI) 4. 4 Thylakoid Membrane – Location of the ETC (Non-Cyclic Photophosphorylation) 7 Chlorophyll A has a porphyrin ring with Mg2+ atom inside – Structure which absorbs light 5. 5 Thylakoid lumen – Location of photolysis. H+ ions accumulates due to ETC 1 6. 6 Intermembrane Space 8 7. 7 Inner Membrane 8. 8 Stroma – Location of the Calvin Cycle 9. 9 Stroma Lamellae – Location of Cyclic Photophosphorylation 9 Steps of Photosynthesis Light Reaction Dark Reaction (aka Calvin Cycle) The electrons (e-) trapped by PSII are energized by light Purpose: Fixes Carbon Dioxide (CO2) into glucose (2 G3P). 2 excited e- are passed to a primary e- acceptor and move through the Electron Transport Chain (ETC) 1. 1 Carboxylation: 6 CO2 + 6 RuBP à 12 PGA 1 These 2 e- lose their energy, which is used to form ~ 1.5 ATP Reaction is catalyzed by the enzyme RuBisCo. The ETC ends at PSI. E- are re-energized and passed to a different primary 2. 2 Reduction: 12 ATP + 12 NADPH converts 12 PGA to 12 G3P or e- acceptor. E- can now either go through the cyclic or non-cyclic path: 12PGAL The byproducts, NADP+ & ADP, go into non-cyclic 3 2 Cyclic Phosphorylation Non-Cyclic Phosphorylation photophosphorylation. 2 e- from PSI go back through the 2 e- go through an ETC and 3. 3 Regeneration: 6 ATP convert 10 G3P to 6RuBP 1st ETC and generate 1 ATP combine with NADP+ & H+ to 4. 4 Carbohydrate Synthesis: Remaining 2 G3P used to form glucose form NADPH These 2 e- are recycled into PSI and can either go through the This NADPH is used in the Calvin The Calvin cycle is light independent; however, it requires cyclic or non-cyclic pathway again Cycle to create glucose the high energy molecules, NADPH & ATP, produced in 4 the light reaction. Action Spectrum Photolysis Chemiosmosis Alternatives to C3 Photosynthesis Chloroplasts are highly H2O splits into 2H+, 2e-, and ½ O2. Uses H+ gradient to create ATP. C4 Photosynthesis CAM Photosynthesis effective at absorbing + + 2H is used for NADPH formation H accumulates in the thylakoid lumen: Alters location of photosynthesis Alters timing of photosynthesis red and blue light. The 2 e- lost in PSII is replenished 1. H+ is released into the lumen through photolysis through this process 2. Between PSII and PSI, Cytochromes bring H+ into the lumen CO2 moved to bundle sheath cells to Fixes CO2 at night instead of Green wavelengths ½ O2 is released as gas from the stroma. This creates a pH and an electrical gradient minimize photorespiration & H2O loss day to minimize are reflected, making it photorespiration & H2O loss least effective at Photolysis occurs at PSII. ATP Synthase uses a gradient to turn ADP into ATP Produces an intermediary 4-carbon photosynthesis. This ATP is used in the Calvin Cycle to create glucose compound & uses 1 extra ATP Chemiosmosis occurs across the Thylakoid membrane.