Biology Review

Biology Review - Omar Khan Study Guide Exam 2...

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Omar Khan Study Guide Exam 2 Photosynthesis (Chapter 9) Photosynthesis depends of light for its reaction A wavelength is the distance from one wave peak to the next Electromagnetic Spectrum o 380-760 nm visible spectrum o violet (shortest); red (longest) Shorter wavelength have higher energy than longer wavelengths Reaction Mechanism: o Light excites electron which causes them to move to higher energy levels o Electron can either return to its ground state, releasing its energy via light/heat o The energized electron may be accepted by an electron acceptor molecule Redox Reaction- Water (Oxidized) Carbon(Reduced) Chloroplasts o Located inside the leaf in the cells of the mesophyll o Stroma - fluid filled region enclosed by the chloroplasts inner membrane o Thylakoids - flat, disclike sacs located in the stroma Thylakoid Lumen- fluid filled region enclosed by the thylakoid inner membrane Thylakoid Membrane o Contain pigments that absorb light at different wavelengths o Chlorophyll- main pigment of photosynthesis- absorbs primarily blue and red wavelengths Porphyrin Ring- a complex ring which absorbs light energy- contains magnesium in the center Also contains a long chain which makes it nonpolar Chlorophyll A- pigment that initiates light-dependent reaction (bright green) Functional group contains a methyl Chlorophyll B- accessory pigment (yellow-green) Functional group contains a carbonyl group Carotenoids - absorb different wavelengths of light than chlorophyll Energy is usually transferred over to chlorophyll a pigment Light-Dependent Reaction o Occurs in the thylakoid membrane
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o ATP and NADPH are products of the reaction o Mechanism: Energized electron transfers onto an electron acceptor Water donates its electron to the electron acceptor causing the water molecule to split Once water splits, oxygen is released The energy of the electron turns ADP into ATP and reduces NADP to NADPH o Chlorophyll a and b are associated with pigment-binding proteins, antenna complexes. The antenna complex absorbs the light energy and transfers it to a reaction center . Light energy is converted to chemical energy in the reaction centers Photosystem I- contains a pair of chlorophyll a molecules with an absorption peak at 700 nm Photosystem II-contains a pair of chlorophyll a molecules with about 680 nm absorption o Non-Cyclic Electron Transport Associated with photsystem I Mechanism: Absorbed energy reaches the reaction center, and excited an electron. Electron is then transferred to a primary electron acceptor. Then its passed through an electron transport chain The electron reduces NADP to NADPH, which is released into the stroma. The missing electron lost during the transfer onto an
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Biology Review - Omar Khan Study Guide Exam 2...

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