Photosynthesis CAQ

🍃 Photosynthesis Advantages of having light harvesting complexes embedded in membrane The photo systems and cytochromes held close to each other In thylakoid membrane, facilitating sequential flow of electrons from photosystem II to cytochrome to photosystem I during light independent reaction The ATP synthases are held in the thylakoid membrane such that ATP synthesis would occur on the Stroma side of the thylakoid where ATP is needed for light independent reactions of photosynthesis Describe photosynthesis Photosynthesis is the process wheee a plant makes sugar from sunlight, water and carbon dioxide, made up of 2 stages which is light dependent and light independent reaction Light energy from sun is converted into chemical energy in plant Light dependent reaction takes place in the thylakoid membrane of the chloroplast During non-cyclic phosphorylation, a photon of light stricken the accessory pigment molecule in a light harvesting complexes in PSII, exciting an electron As the excited electron drop to ground state The energy released is then passed on to neighbouring pigment molecules down an energy gradient until it reaches to P680 chlorophyll a molecules in the reaction centre of PSII One electron of the P680 molecules is excited to a higher energy level and captured by primary electron acceptor in PSII causing an electron hole in the reaction centre and the electron displaced from the reaction centre is replaced by photolysis of water which takes place in the thylakoid space forming oxygen as a by product Phot osynthesis 1

Each photo excited electron is passed down a series of increasingly electronegative electrons carriers from primary electrons in PSII to PSI via an electron transport chain and the high energy electron loses energy as it travels down the electron transport chain The energy released is used to actively pump H from the storms into the thylakoid space against the concentration gradient, creating a proton gradient so that the H ions can diffuse down the proton gradient from the thylakoid space and into the stroma via ATP synthase and then phosphorylating ADP to ATP Accessory pigments in the light harvesting complex of PSI also receives photons and excites an electron of one of the two P700 chlorophyll a molecules and the electron is captured by the primary electron acceptor in PSII The electron loser is replaced by by electrons from the electron transport chain form PSII The displaced electron in OAI is passed down a second electron transport chain and accept by NADP reductase to reduce NADP to NADPH In cyclic phosphorylation, electrons do not pass through PSII but instead electrons displaced from PSI are transferred to the primary electron acceptor in PSI and then to the electron transport chain between PSII and PS I and back to PS I, NADPH not produced but ATP synthesis will still occur via chemiosmosis in the same manner as non-cyclic photophosphorylation The light Independent re