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Chloroplasts Lab Report

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Questions and Hypotheses

Experiment 1 Question: The main question that was addressed in the first experiment (Parts I and II) was which cell fraction had the most photosystem activity, which would be proportional to the number of chloroplasts present in the cell fraction. Photosystem activity is proportional to the number of chloroplasts since the photosystems are active in the thylakoid membranes of chloroplasts (Leicht and mcallister 2016). The amount of photosystem activity would be seen in the relative absorbance values for each cell fraction under the given light conditions. The absorbance would decrease as the DCIP electron acceptor (which is blue when oxidized) gets reduced (which is colorless). “The amount of color change is expected to be proportional to the number of functional photosystems, which in turn is proportional to the number of intact chloroplasts” (Leicht and mcallister 2016). We knew that chloroplasts were required for photosystem activity, but we …show more content…

Figure 3 shows the absorbance readings of P2 broccoli cell fraction under the following light conditions: white light, red light, blue light and green light. Based on the data in Figure 3, we can see that both red and blue light decreased in absorbance while green light had a slight change in absorbance. Figure 4 is related to Figure 3 because Figure 4 shows the total change in absorbance of each of the specific light conditions. The data from Figure 4 was calculated by finding the difference in the final (7 minutes) and initial (0 minutes) absorbance values for each of the light conditions in Figure 3. Based on the data in Figure 4, it can easily be seen that red light had a higher change in absorbance than blue light, and it can also be determined that green light had no decrease in absorbance. Compared to the positive control, red light had the most change in absorbance which means it had the most reduction of

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