Photosynthesis 4/19/2019

Introduction Photosynthesis Photo--”light” The process of storing energy from the sun in the form of glucose The process of making sugar (glucose) using light energy Photo--”light” Synthesis--”make” ; “put together” 4/19/2019

Introduction Nourishes almost all of the living world directly or indirectly Autotroph Organism that obtains organic food molecules without eating other organisms. Use energy from the sun or from oxidation of inorganic substances to make organic molecules from inorganic ones. 4/19/2019

Introduction Hetereotroph An organism that obtains organic food molecules by eating other organisms or their by-products Fungi on feces, carcasses Bacteria 4/19/2019

Photosynthesis Chemical Reaction 6CO2 + 12H2O + Light Energy --> C6H12O6 + 6O2 + 6H2O 4/19/2019

Structure of the Leaf Site of Photosynthesis Chloroplasts are the sites of photosynthesis in plants Chloroplasts contain chlorophyll A green pigment that captures light energy during photosynthesis Found in the cells of the mesophyll of the leaves Stomata Pores under the leaves where CO2 enters and O2 leaves the plant/leaf 4/19/2019

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Events of Photosynthesis The Light Reactions Photo part of photosynthesis Calvin Cycle Synthesis part What do we synthesize? 4/19/2019

Light Reactions Photo part of photosynthesis Convert solar energy to chemical energy Contains the photo systems that cooperate in the light reactions of photosynthesis Each photosystem will absorb specific wavelengths of light Photosystem I--700nm Photosystem II--680 nm Oxygen is formed in photosystem II H2O is a reactant in the formation of O2 4/19/2019

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ATP & NADPH ATP is produced at Electron Transport Chain #1 NADPH is produced at Electron Transport Chain #2 ALL ATP and NADPH produced during the Light Reactions are transported to the Calvin Cycle to be used in the synthesis of glucose 4/19/2019

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Light Reactions I Overall Inputs Light NADP+ ADP P H2O Outputs ATP NADPH O2 4/19/2019

Light Reactions Sequence of Events Non-Cyclic Flow Photosystem II The reaction center drives an oxidation-reduction reaction (Redox Reaction) that helps in the formation of oxygen. Electron Transport Chain I ATP produced will be used in the Calvin Cycle Photosystem I Continues the movement of electrons Electron Transport Chain II NADPH produced will be used in the Calvin Cycle 4/19/2019

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Non-Cyclic Electron Flow Uses both photosystems Produces NADPH, ATP and oxygen 4/19/2019

Cyclic Electron Flow Only uses photosystem I and part of Electron Transport Chain I Produces ATP but no NADPH or O2 Used to “make-up” the necessary amount of ATP’s for the Calvin Cycle 4/19/2019

Calvin Cycle “Dark Reactions” Synthesis of photosynthesis Makes sugar Uses ATP and NADPH to convert CO2 to sugar 4/19/2019

Calvin Cycle Overall Inputs Outputs CO2 H2O ATP NADPH Sugars (Glucose) 4/19/2019

Calvin Cycle Sequence of Events Carbon Fixation Use of carbon dioxide Reduction 1, 3 bisphosphoglycerate is reduced to the sugar G3P 6 ATP’s is used Reduced using the electrons produced by the oxidation of NADPH Regeneration of CO2 Acceptor This acceptor, RuBP, is then re-used in carbon fixation to continue the next cycle of the Calvin Cycle 4/19/2019

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