生物化学原理教学（杨荣武）Chapter26 Photosynthesis.pptVIP

Chapter26 Photosynthesis Photosynthesis The Power of Green Overview of Photosynthesis The structure of the chloroplast The Nature of Light Chlorophyll and Accessory Pigments Photosystems Stages of Photosynthesis (1) The Light Reactions -Formation of ATP and NADPH (2) The Dark Reaction -The Calvin Cycle Photorespiration Regulation of photosynthesis Photosynthesis Site of Photosynthesis Pigments: Center pigment: specialized chlorophyll a acting as the reaction center in the PS Antenna pigments (accessory pigment) : other chlorophyll a chlorophyll b and chlorophyll c, Carotenoids -carotene lutein,anti-oxidants, protect the chlorophyll,Phycobilins Photosystems: discrete units of pigment organization in the thylakoid membrane PSI: P700; PSII:P680 A photon-excited molecule can dissipate its excitation energy in a variety of ways Internal conversion: The energy of the excited state (an electron in a high energy orbital) is converted to heat. Fluorescence: The energy of the excited state is lost by emitting a photon. Exciton transfer: (resonance energy transfer): The energy of the excited state is transferred to nearby unexcited molecules with similar electronic properties. Photooxidation: The excited molecule loses an electron (becomes oxidized) to an acceptor molecule (becomes reduced). These last two processes are important in photosynthesis Absorption of light by pigments Photosystems and Reaction Center Photosystems are functional and structural units of protein complexes involved in photosynthesis that together carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons. At the heart of a photosystem lies the Reaction Center, which uses light to reduce molecules. In a photosystem, this Reaction Center is surrounded by light-harvesting complexes (LHC) that enhance the absorption of light and transfer the energy to the Reaction Centers. Light-Harvesting and Reaction Cent