BCHM 307 1st Edition Lecture 39 Outline of Last Lecture I Photosynthetic Energy II Light Energy into Chemical Energy A Three Conditions III Chloroplasts IV Absorbance Spectrum Outline of Current Lecture I Photosynthetic Energy and Light II Light versus Dark Reactions III Electron Transport Chain IV Photosystems Current Lecture This lecture continues on with photosynthesis First we will look at the reactions that make up photosynthesis The photosynthetic electron transport process occurs in the thylakoid membrane of the chloroplasts It uses integral membrane complexes and pigments to accomplish this Chlorophyll and accessory pigments funnel the energy towards the photosynthetic reaction center This energy can come from two different places The reaction center can be excited by light directly The other option is to funnel in resonance energy from neighboring pigments that have been excited by light When the reaction center become excited the redox potential is increased An increased redox potential is more negative numerically The reactions that encompass photosynthesis can be broken into two categories These two types are light and dark reactions They are not only physically separate but also chemically separate The light reactions depend on light directly This reaction is as follows 2 H2O 2 NADP yields 2 NADPH 2 H O2 coupled with ADP Pi yields ATP H2O The dark reactions don t directly depend on light absorption Contrary to the name they do take place during the day time These reactions are also called carbon dioxide fixing reactions They dark reaction equation is as follows Co2 2 NADPH 2 H yields 2 NADP CH2O H2O This is also coupled with an ATP production reaction These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute The photosynthesis electron transport process begins with water which is an extremely weak reductant This won t be able to properly reduce NADP Therefore light energy must be captured This light energy will elevate the redox potential in the electrons of water The purpose of the electron transport chain is to elevate the redox potential in the various electrons There are two main centers in the photosynthetic electron transport chain These are called photosystem I and photosystem II Photosystem II is actually the first one to be encountered It has an optimal wavelength of 680 nm which is red light The other photosystem has an optimal wavelength at 700 nm The light hits these photosystems in order to elevate the electrons redox potential The way the electrons become raised in redox potential a diagram of this process is often referred to as the Z scheme The whole Z scheme process is compartmentalized within the chloroplast
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