Biology Chapter 7 Photosynthesis

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Assignments:21. Go to the following Web site:http://photoscience.la.asu.edu/photosyn/study.htmlThis is an essay on the importance of photosynthesis. Read this to get a sense of the many ways weare dependent on this process.2. Go to the following Web site:http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.htmlI. <strong>Photosynthesis</strong>A. Energy and materials for the reaction1. The light-dependent reaction (Rxn) converts light energy to chemical energy(which is then stored in ATP)+ +a. Liberated electrons and protons (H ) from water are picked up by NADP2. The light-independent Rxn assemble sugars and other organic moleculesa. Using ATP, NAPDH and CO 23. Overall for Rxn for the synthesis of sugar:B. Where the Rxn takes placeH2O + CO 2 6O 2 + C6H12O61. The two stages of photosynthesis take place in the chloroplast2. Light dependent Rxn occur in the thylakoid membrane systema. The thylakoids are folded into grana (stacks of disks) with channels.b. The interior spaces or lumen of the thylakoid disks and channels arecontinuous.3. Carbohydrate formation occurs in the stroma (semifluid) area thatsurrounds the granaII. Light-Trapping pigmentsA. Light energy is packaged as photons, which vary in energy as a function of wavelength
1. Plants use only a small range (400 - 750 nm) of wavelength for photosynthesis32. Most of these wave lengths are the ones we see as visible colorsB. Pigments absorb light energy and give up electrons1. Chlorophyll pigments absorb blue and reda. Reflect green (the color of leaves).2. Carotenoid pigments absorb violet and bluea. Reflect yellow, orange, and red.III. Light-dependent RxnA. Three event occur:1. Pigments absorb sun light energy and give up electrons2. The pigments that gave up the electrons in the first place get electron replacements3. Electron and hydrogen transfers from water leads to ATP and NADPH formationB. Photosystems1. A photosystem is a cluster of 200 to 300 light-absorbing pigmentslocated in the thylakoid2. The pigments ‘harvest’ sunlighta. Absorbed photons of energy boost electrons to a higher energy levellb. The electrons quickly return to the lower level and release energyc. Released energy is trapped by chlorophylls, which act as a sink for energy harvestedby all pigmentsd. The trapped energy is then used to transfer a chlorophyll electron to an acceptor moleculeC. ATP and NADPH loading up energy, hydrogen and electrons1. Electron transport system are organized in a sequences of enzymes and other proteinsbound in thylakoid membranea. Electrons extracted from H2O by the chlorophyll molecule pass through one or twoelectron transport systems in the thylakoid membrane to produce NADPH from NADP ++b. The flow of H through the thylakoid membrane drives the formation of ATP
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Biology Chapter 7 Photosynthesis

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