Photosynthesis Packet #30 Chapter #10

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” 11/20/2018

Introduction II Nourishes almost all of the living world directly or indirectly Based on the food chain/web More to come later in the course Chemical Equation for Photosynthesis 6CO2 + 12H2O + Light Energy --> C6H12O6 + 6O2 + 6H2O 11/20/2018

Structure of Leaf

Structure of Chloroplasts

Events of Photosynthesis The Light Reactions Photo part of photosynthesis Calvin Cycle Synthesis part Sugar is synthesized 11/20/2018

Light Reactions

Light Reactions “Photo” part of photosynthesis Convert solar energy to chemical energy Composed four distinctive parts Photosystem II Electron Transport Chain I Photosystem I Electron Transport Chain II 11/20/2018

Light Reactions II The goal of the light reactions is to produce ATP and NADPH via the movement of electrons The ATP, and NADPH, produced is used in the Calvin Cycle.

Photosystems The photosystems first responsibility is to absorb light. Photosystem II Absorbs light with wavelengths of 680 nM Photosystem I Absorbs light with wavelengths of 700 nM The second function of the photosystems is to remove electrons and then move them to the electron transport chains. Special Note Oxygen, a waste product as a result of photosynthesis, is produced by the removal of electrons from H2O in photosystem II

Photosystems II Photon, of a specific wavelength, hits a chlorophyll molecule and causes an electron to become excited.

Photosystems III The excited electron bounces around until it reaches special chlorophyll molecules located in the reaction center. Electrons, once in the reaction center, move to the primary electron acceptor. Electrons then move onto an electron transport chain.

Light Reactions I Overall Inputs Light NADP+ ADP P H2O Outputs ATP NADPH O2 11/20/2018

Light Reactions The Flow of Electrons Cyclic vs. Non-cyclic Flow

Non-Cyclic Electron Flow Non-cyclic electron flow, as the name implies, is the movement, and use of electrons, once through the parts of the light reactions, to produce ATP and NADPH. All four parts (steps), of the light reactions, are used.

Non-Cyclic Electron Flow I Photosystem II The reaction center drives an oxidation-reduction reaction (Redox Reaction) that helps in the formation of oxygen. 11/20/2018

Non-Cyclic Electron Flow II Electron Transport Chain I ATP produced will be used in the Calvin Cycle 11/20/2018

Non-Cyclic Electron Flow III Photosystem I Continues the movement of electrons 11/20/2018

Non-Cyclic Electron Flow IV Electron Transport Chain II NADPH produced will be used in the Calvin Cycle 11/20/2018

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 11/20/2018

The Calvin Cycle “Dark Reactions”

Calvin Cycle “Dark Reactions” Synthesis of photosynthesis Makes sugar ATP and NADPH are used to convert CO2 to sugar 11/20/2018

Calvin Cycle Overall Inputs Outputs CO2 H2O ATP NADPH Sugars (Glucose) 11/20/2018

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 11/20/2018

Calvin Cycle I Carbon Fixation

Calvin Cycle II Reduction

Calvin Cycle III Regeneration of CO2 Acceptor