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9/20/2016 Bio100 (Paddack) Lecture 8 (9/19/16): Photosynthesis I. Photosynthesis A. Sunlight B. Anatomy of leaf C. Photosynthesis (C3 pathway) 1. Light reaction i. Capture photon ii. Use energy from photon to split water iii. Use electron from splitting water to synthesize ATP & NADPH 2. Calvin cycle i. Uptake of CO2 ii. Synthesis of 3-C compound (PGA) iii. Synthesis of 6-C compound (glucose) D. Photosynthesis constraints & solutions 1. C4 photosynthesis (spatial separation of cycles) 2. CAM photosynthesis (temporal separation of cycles) Photosynthesis Photoautotrophs- Organisms that use the sun’s energy to make food Trees, flowers Wheat Algae (a Protist) Cyanobacteria Fig. 7.1 In plants and algae, photosynthesis occurs in chloroplasts 1 9/20/2016 Figure 5.6 Absorption Spectra of Plant Photosynthetic Pigments Figure 7.6B The Light Reactions • Photons hit chlorophyll molecules – This knocks electrons to a higher energy level The Light Reactions • A Reaction Center captures the energy from excited electrons Figure 7.7B Figure 7.7A The Light Reactions • Electrons are passed through an Electron Transport Chain to produce ATP and reduce NADP+ to NADPH ATP is produced through Chemiosmosis! Figure 7.9 Figure 7.9 2 9/20/2016 Light Reactions Summary of the Light Reactions… H2 O Dark Reactions ½ O2 + 2 H+ Transferred to Light Energy NADPH ATP The Dark Reactions (The Calvin Cycle) • Requires energy from ATP and NADPH • Takes carbon from CO2 to make G3P • Glucose is made from 2 G3P Figure 7.10 3 9/20/2016 C4 Cycle Figure 5.17 Examples of Plants with the CAM Photosynthetic Pathway Figure 5.16 Crassulacean Acid Metabolism (Part 1) Figure 5.16 Crassulacean Acid Metabolism (Part 2) Figure 5.15 C3, C4, and CAM Photosynthesis Compared Calvin Cycle 4 9/20/2016 Lecture 8 (9/19/16): Photosynthesis 1. Define: wavelength, photon. 2. Be able to identify the following structures of plants & state the function of each: stomata, mesophyll cells, chloroplast, thylakoid, stroma, chlorophyll. 3. Write the chemical equation for photosynthesis. 4. What does ‘carbon fixation’ mean? 5. List the 2 stages of photosynthesis, noting what each stage does and what comes out of it. 6. What physical environmental condition have C4 & CAM plants been able to overcome? Briefly, how do they get around this problem? 5