Chlorophenolindophenol Hill Reaction

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Abstract The purpose of this experiment was to measure the effects of 2,6-dichlorophenolindophenol (DCMU), ammonia, light intensity, and light color on the Hill Reaction in isolated chloroplasts. Chloroplasts were separated from spinach using the centrifugation technique. The chloroplasts were mixed with different proportions of ammonia and DCMU to distinguish between uncouplers and inhibitors to the electron transport in photosynthesis. The second experiment tested for the effects of light intensity and color. Different distances and colored film were used to measure the reaction rate of photosynthesis in different conditions. The results from these tests were that DCMU was an inhibitor and ammonia the uncoupler. The optimal distance tested…show more content…
The results are shown below. Table 3: This table shows the raw data (absorbance) for the experiment testing for the effects of light intensity on the Hill Reaction. Time (min) Tube 0 1 2 3 4 5 15 cm 0.356 0.281 0.207 0.143 0.096 0.053 25 cm 0.377 0.283 0.236 0.202 0.145 0.097 35 cm 0.380 0.283 0.271 0.258 0.245 0.232 45 cm 0.342 0.267 0.233 0.184 0.146 0.134 Figure 2: This figure shows the change in absorbance for each tube versus the time in minutes. The slopes of each line (shown in the four equations in the figure) are the rates of each reaction. The tubes at 15 cm, 25 cm, and 35 cm followed the trend of increasing distance means decreasing light intensity. However, the tube at 45 cm showed a reaction rate between that at 25 cm and 35 cm. Effect of Light Color on the Hill Reaction Table 4: This table shows the raw data (absorbance) for the experiment testing for the effects of light color on the Hill Reaction. Time (min) Tube 0 1 2 3 4 5 Red 0.363 0.339 0.283 0.217 0.175 0.141 Blue 0.397 0.378 0.364 0.348 0.327 0.313 Yellow 0.392 0.318 0.260 0.199 0.151 0.123 Green 0.343 0.335 0.329 0.326 0.315…show more content…
Each measurement was around the same absorbance of 0.350 at the 0 minute mark. Effect of Light Intensity on the Hill Reaction As stated earlier, the equation for light intensity is I=1/d2. As the distance of the light increases, the intensity decreases. The more intense the light is, the more willing electrons will be to become excited (the first step of photosynthesis). The results from figure 2 matched this assumption for the most part. The rates at 35 cm and 45 cm were opposite of what was expected. The 45 cm sample reacted quicker than the 35 cm sample. This could be a result of improper procedure when filling each sample or influence of outside light. Effect of Light Color on the Hill Reaction The color of light can also affect the rate of the Hill Reaction. Different chlorophylls in the plant absorb and use different wavelengths (colors) of light. Chlorophyll a is considered to be the most important due to its role in absorption. It should absorb blue light the best and green or yellow light the

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