Essay Example on Photosynthesis is the process of which plants convert sunlight Water








Photosynthesis is the process of which plants convert sunlight water and into a 5 base glucose sugar used for food They use their chloroplasts to do this process there are two stages light dependent and light independent Light dependent takes place in the thylakoid within this thylakoid is a small space separating between each one a full stack of thylakoids are called a Granum this is but one part of photosynthesis In this report I will explain in full detail about the process of photosynthesis and what it takes to perform this function LIGHT REACTIONS There are two parts used to convert light energy and water into glucose light reactions and the Calvin cycle The light reactions take in water and split it into two oxygen and take in the hydrogen light reactions take in water and split it into 02 and H CO2 2H2O photons CH2O O2 H2O NADPH is then carried over into the Calvin cycle as shown in this diagram Light absorbed by chlorophyll drives a transfer of electrons and hydrogen from water to an acceptor call NADP Water is split in this process and because of this process oxygen 02 is then released as a by product of light reactions LIght reactions use solar power to reduce NADP to NADPH by adding a pair of electrons to the hydrogen molecule or H Including the NADPH carried over from the light reactions it also transfers ATP Light reactions make ATP using chemiosmosis to power the addition of a phosphate group to ADP created by the Calvin cycle this process is called photophosphorylation

THE CALVIN CYCLE AND LIGHT REACTIONS WORKING TOGETHER The Calvin cycle is the second part of photosynthesis as you have already read the Calvin cycle gives off and transfers NADP ADP and Pi to the light reactions As we can see in this example the Calvin cycle gives of these molecules as energy and tools for the light reactions in order to convert the water into oxygen After this process is complete the light reactions attack a hydrogen molecule to NADP the same hydrogen from the water in order to be added to the sugar made by the Calvin cycle Light reactions then convert the light into ATP for the Calvin cycle as energy The Calvin cycle then converts CO2 into CH20 or a 5 base carbon sugar this process of converting carbon into organic compounds and known as carbon fixation HOW THE LIGHT REACTIONS MAKE ATP AND NADPH Chlorophyll molecules supercharged by absorbing light energy act different inside of a chloroplast then they do normally In their normal environment they are surrounded by other small organic molecules and proteins into a photosystem A photosystem is made up of a reaction center and surrounded by light harvesting complexes Each light harvesting complex consists of a pigment molecule bound together to specific proteins These act as an antenna and hold and transfer more light energy than any single pigment could This is so the energy goes straight to the reaction center The reaction center holds two special chlorophyll A molecules and a primary light acceptor the special molecules use the energy from the light to supercharge one of their electrons Light drives the creation of NADPH and ATP by charging the two photosystems inside the thylakoid membranes 

The key to this a flow of electrons throughout the whole process There are two ways this flow can go cyclic and noncyclic In a noncyclic flow the light hits the pigments until it reaches the P680 or the special molecule inside the reactions center it uses the light send an electron to the primary acceptor as this happens the water molecules are split and an electron is taken and sent to the specific molecule The electron is sent from photosystem 1 to photosystem thought and electron transport chain made up of plastoquinone then some electrons fall to a lower level of energy for the creation of ATP Then the electron is sent to the other special molecule and back to the acceptor and to NADP reductase through a chain but with ferredoxin the electron is then transferred The reductase takes two electrons of the ferredoxin and a hydrogen ion from the stroma in order to create NADPH within the NADPH the electrons are stored with a lot of energy the NADPH will then be given to the Calvin cycle All of this is shown in the picture below CYCLIC ELECTRON FLOW Sometimes charged electrons take a different path called cyclic electron flow which uses Photosystem 1 but not Photosystem 2 this allows for more productions of ATP Unlike the noncyclic flow which makes both ATP and NADPH in equals parts this makes more ATP This is needed because the Calvin cycle consumes more ATP than NADPH HOW ATP IS MADE WITHIN THE THYLAKOID SPACE Within the stroma the low hydrogen concentration is taken through the electron chain to the ATP synthase

The fallen electrons are used to power the process it takes the hydrogen ion and uses diffusion to combined ADP and PI creating ATP CALVIN CYCLE USES ATP AND NADPH TO MAKE CO2 TO SUGAR First it takes in one carbon at a time and attaches it to a five carbon sugar called ribulose bisphosphate after this rubisco comes in and catalyzes it and forms an unstable six carbon intermediate then it immediately splits in half making two molecules of 3 phosphoglycerate Each molecule of 3 phosphoglycerate gets another phosphate group from ATP Becoming 1 3 bisphosphoglycerate Next a pair of electrons donated from NADPH reduces 1 3 phosphoglycerate to g3p the sugar output After this one of the 6 g3p s uses three more molecules of ATP becomes ribulose bisphosphate After using the electron from NADPH it becomes NADP and PI including an ATP turned into an ADP then all that is given to the light reactions and the whole process start over again

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