BIO204 CH10 - Photosynthesis - Lecture 4

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Sanja Hinic- Frlog

4 (CH10 - Photosynthesis) October-09-13 8:30 PM Key Concepts - Photosynthesis • Photosynthesisconsists of two linked sets of reactions ○ Light reactions / light-dependent reactions  Transformationof solar (photons) to chemical energy (electrons)with high potential energy  Use of electrons to produce ATP and the electron carrier NADPH ○ Dark reactions / light-independent reactions of the Calvin cycle (occur in different locations)  ATP and NADPH are used in the Calvin cycle to reduce carbon dioxide (CO ) to2 carbohydrate • In eukaryoticcells, both processes take place in chloroplasts • Autotrophs - "self-feeders"or photosyntheticorganisms • Heterotrophs - "different-feeders" Introduction to Photosynthesis • Photosynthesisis the process by which plants generate organic from inorganic compounds in the light Photosynthesis in daily life • Food • Fossil and bio-fuels from photosynthesis • Plant secondary products in pharmaceutical products (e.g. astaxanthin, chlorophyll) • Global Change - removal of CO fr2m atmosphere Photosynthesis – a biological oxidation – reduction process • Conversionof species low in energy into energy enriched carbohydrates and O 2 • Conversionof solar radiation into chemical energy • Glucose (C H6 12 i6 the typical carbohydrate Sucrose is most commonin plants  It is the transport form The carbon and oxygen cyclein the atmosphere and the cell Photosyntheticreaction is the reverse cellular respiration Photosynthesis: Electrons link two sets of reactions • Two sets of reactions ○ light-dependent reactions produce oxygen gas (O ) fro2 H O 2 ○ light-independent reactions of the Calvin cycle or dark reactions produce sugar from CO 2 • Reactions linked by electrons ○ Electrons released in the light-dependent reactions when water is split to form O + 2 ○ Electrons then transferred to the electron carrier NADP , forming NADPH • Calvin cycle uses NADPH to reduce CO 2 • ATP resulting from the light-dependent reactions is also used in the Calvin cycle to make sugars Calvin cycle • Melvin Calvin, Andrew Benson, James Bassham • 1950‘sUniversity of California, Berkeley 14 • Used radioisotope CO 2 ○ Tracer experiments ○ Mapped the route of CO du2ing photosynthesis • 1961 Nobel Price in Chemistry The sun - The ultimate source of energy What is solar radiation? • Solar spectrum includes whole electromagneticspectrum • Earth atmospheretransparent only for part of infrared, ultraviolet and visible light The nature of light – particles and waves • Light - electromagneticradiation • Light - electromagneticradiation • Acts as a wave & a particle • Wave - light can be characterized by its wavelength - the distance between two successive wave crests ○ Shorter wavelengths(e.g., blue, ultraviolet) have moreenergy than longer wavelengths (e.g., red, in
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