Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Biology 113 Photosynthesis:Transformation of Energy History of Photosynthesis; Light and Color OBJECTIVES: To understand the basic concepts associated with energy transformations, including the Laws of Thermodynamics that govern energy transformations. To understand the chemical nature of photosynthesis. To understand the history of our understanding of photosynthesis. To master basic concepts associated with the nature of light To understand how pigments work. To understand how photosynthesis evolved. Energy potential energy vs. kinetic energy kinds of energy - thermal, light, electrical, mechanical, chemical First Law of Thermodynamics (Law of the Conservation of Energy) Second Law of Thermodynamics (Law of Entropy) exergonic vs. endergonic chemical reactions; enzymes, coenzymes and cofactors energy in open vs. closed systems Chemical Nature of Photosynthesis Oxidation - Reduction Reactions in General chlorophyll 6CO2 + 12H2O ---------> C6H12O6 + 6O2 + 6H2O ; Equation for Photosynthesis light Enzymes, cofactors and coenzymes energy of activation ATP/ADP – the universal energy exchange system in living organisms coupled reactions: endergonic rxn + ATP + ATPase --> exergonic reaction History of Photosynthesis van Helmont's willow tree experiments (1648?) Priestley's method of "restoring air" (1771) Ingenhousz experiments - light are green plants are necessary for “restoring air” (1778) Englemann's experiment (1882) van Niel's observations (1920's): 6CO2 + 12 H2S --------=> C6H12O6 + 12S + 6H2O purple sulfur bacteria light Hill Reaction – isolated chloroplasts if given an electron acceptor will generate 02 Ruben and Kamen - verify that the O2 in photosynthesis comes from water (1941) Light electromagnetic spectrum = radiant energy gamma - X-rays - UV - violet - blue - green - yellow - orange - red - infrared - radio 10 380 nm 500 nm 750 nm 10 visible light - 380-750 nm - biologically active (some use infrared & some use UV) light as a wave phenomenon; velocity (speed of light) = wavelength X frequency light as a particle; energy = Planck’s constant X speed of light / wavelength photons and quanta of light Chlorophyll and light absorption pigment - a substance that absorbs visible light porphyrin ring (conjugated bonds uniting 4 pyrole rings around a central chlorophyll molecule, with a long insoluble carbon-hydrogen chain which anchors the molecule) light absorption -->heat or heat and light (fluorescence) or resonance energy transfer or transfer of a high-energy electron (leaving an electron “hole”) absorption spectrum for chl. a, chl. b, and carotenoids (carotenes and xanthophylls) action spectrum for photosynthesis accessory pigments in Kingdom Plantae - chl. b, carotenes, xanthophylls motile aquatic bacteria, bacteriorhodopsin and evolution of photosynthesis color