Light Dependent Reaction
- Ultraviolet radiation from the sun excites the electrons in the thylakoid membrane of the chloroplast.
- The electron is excited and jumps an energy level so it is emitted and joins the electron transport chain
- As the electron passes along the electron carriers a series of oxidation reactions occur.
- This releases energy which is used in the photophosphorylation of ADP into ATP
- Within the thylakoid space an enzyme catalyses the photolysis of water to give 1/2O2, 2H+, and 2e- when PSII loses electrons.
- The electrons replace those lost in the chlorophyll molecule in order to allow the flow of electrons to continue and restore it so it’s no longer positively charged.
- The hydrogen ion concentration within the thylakoid space is raised as a result of photolysis.
- The electrons that have passed along the electron transport chain combine with the co-enzyme NADP and hydrogen ions from the water to reduce NADP into NADPH/reduced NADP.
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Light Independent Reaction
- Carbon diozide combines with 5-carbon molecule called RuBP catalyzed by RuBISCO to form 6-carbon molecule.
- It is unstable and immediately breaks down into 2 3-carbon molecules called GP
- GP is reduced via the hydorgen from reduced NADP to form GALP. ATP from light dependent reaction provides energy for reaction.
- 2 out of 12 GALP formed are involved in the creation of Glucose (hexose sugar) which can be converted into starch, cellulose, amino acids, lipids etc
- 10 out of the 12 GALPs are used in the recreation of RuBP as they re-arrange to from 6 5-carbon compounds then phosporylation using ATP reforms RUBP
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