Chemistry for Biologists: Photosynthesis - The Royal …
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Photosynthesis in Plants - Overview of Photosynthesis
Ferredoxin NADP Reductase (FNR) - transfers an electron from each of two ferredoxin molecules to a single molecule of the two electron carrier NADPH.
ATP Synthase - complex that uses the potential energy of flowing hydrogen ions to make ATP
Three Mobile Carriers that transports the electrons:
Plastiquinone Qb - transports the protons to the lumen of thylakoid discs, while the electrons continue through the electron transport chain into the cytochrome b6f protein complex.
Plastocyanin - functions as an electron transfer agent between cytochrome f of the cytochrome b6f complex from photosystem II and P700+ from photosystem I
Ferredoxin - accepts electrons produced from sunlight-excited chlorophyll and transfers them to the enzyme ferredoxin:NADP+ oxidoreductase
Light-independent reaction or Calvin Cycle
Light-dependent: converts light energy into chemical energy; produces ATP molecules to be used to fuel light-independent reaction, NADPH and Oxygen ( O2).
Light-independent: uses ATP produced to make simple sugars.
2 Phases of Photosynthesis
1.) A photon of light hits a chlorophyll molecule surrounding the Photosystem II complex; this creates resonance energy that transferred to neighboring chlorophyll molecules.
2.) When this energy reaches the reaction center embedded in Photosytem II, an electron is released.
One molecule of carbon dioxide is combined with one molecule of …
The NADPH is the main in chloroplasts, providing a source of energetic electrons to other reactions. Its production leaves chlorophyll with a deficit of electrons (oxidized), which must be obtained from some other reducing agent. The excited electrons lost from chlorophyll in are replaced from the electron transport chain by . However, since includes the first steps of the Z-scheme, an external source of electrons is required to reduce its oxidized chlorophyll a molecules. The source of electrons in green-plant and cyanobacterial photosynthesis is water. Two water molecules are oxidized by four successive charge-separation reactions by photosystem II to yield a molecule of diatomic and four ions; the electron yielded in each step is transferred to a redox-active residue that then reduces the photoxidized paired-chlorophyll a species called P680 that serves as the primary (light-driven) electron donor in the photosystem II reaction center. The oxidation of water is in photosystem II by a redox-active structure that contains four ions and a calcium ion; this binds two water molecules and stores the four oxidizing equivalents that are required to drive the water-oxidizing reaction. Photosystem II is the only known biological that carries out this oxidation of water. The hydrogen ions contribute to the transmembrane chemiosmotic potential that leads to ATP synthesis. Oxygen is a waste product of light-dependent reactions, but the majority of organisms on Earth use oxygen for , including photosynthetic organisms.
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