An Investigation of the Effects of Varying Conditions on Light.docx

  • Monash University
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Isabella GalwayAn Investigation of the Effects of Varying Conditions on Light-Dependent Electron Transport Measured by Absorbance of DCPIP in Isolated Silverbeet ChloroplastsIntroductionPhotosynthesis is a process where carbon dioxide (CO2) and water (H2O) are converted into glucose (C6H12O6) and oxygen (O2). Photosynthesis can be divided into two processes, the light-dependent process and the temperature-dependent process. This experiment focuses on the light-dependent process. During this process, light energy is captured by the photosynthetic pigments present in chloroplasts and used to split H2O into protons (H+) and electrons (e-) and O2. H+is used in a process called chemiosmosis to drive ATP formation, while the e-are passed down the electron transport chain, with the result being the formation of NADPH. During this experiment, DCPIP was added to the solutions, which accepts e-. When these e-are accepted, DCPIP loses its colour which can then be measured by absorbance using a spectrophotometer, thus allowing DCPIP to be used as a measure of the rate of photosynthesis. The aim of this experiment was to investigate the effects of different conditions on light-dependent electron transport using DCPIP and isolated chloroplasts from silverbeet leaves, with the results being measured by the absorbance of the solutions containing DCPIP. It was hypothesised that for the dark tube, there would be no decrease in absorption of DCPIP. It was hypothesised that for the tube kept in the light, there would be a significant decrease in absorption of DCPIP. It was hypothesised that for the tube that contained the boiled solution, there would be no decrease in absorption of DCPIP. It was hypothesised that the tube with solution containing DCMU would not show a decrease in absorption of DCPIP. It was hypothesised that the tube wrapped in red cellophane would show a decrease in absorption of DCPIP. It was hypothesised that the tube wrapped in green cellophane would not show a decrease in absorption of DCPIP.

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