Sunday, December 8, 2013

Chromatography & Photosynthesis Lab

Purpose: The purpose of the chromatography lab was to use chromatography to separate and identify pigments and other molecules from cell extracts that contain a mixture of molecules. For the photosynthesis lab, it was to test the rate of photosynthesis in different scenarios. The concepts we were testing was photosynthesis itself and its process of how chlorophyll relates to the color change.

Introduction: Chromatography paper is special paper that is used to separate and identify pigments and other molecules from cell extracts that contain a mixture of molecules. It works by viewing how the solvent travels vertically up paper by capillary action (the attraction of solvent molecules to the paper and other solvent molecules). As the solvent moves up the paper, different pigments are carried up at different rates due to due to their differences in solubility. Photosynthesis is the conversion of solar energy to chemical energy in plants. Plants use that chemical energy to promote cell growth, consume it as a food source, and for other cellular functions. That conversion occurs in the chloroplasts plant cells. The rate at which photosynthesis occurs in chloroplasts depends on the amount of light that plants receive.

Methods: In the chromatography lab, pigments from a spinach leaf were extracted on a piece of chromatography paper and barely immersed in 1ml of solvent. Once immersed, we measured the distances the different pigments in the solvent traveled upward on chromatography paper. In the photosynthesis lab, we measured how the rates of photosynthesis were effected in four cuvettes containing different variations of chloroplasts, when exposed to light. Those variations were unboiled chloroplast (surrounded by tinfoil), unboiled chloroplast (exposed to light), boiled chloroplast (exposed to light), and no chloroplast (exposed to light). Each solution’s absorbance and % transmittance was measured before they were exposed to light. Once measured for the first time, they were placed in front of a light and were removed every five minutes, three times for each cuvette, to be tested for any change in absorbance and % transmittance.

The results of the failed attempt, measured in percent transmittance (photosynthesis lab).

The results of the successful attempt, measured in percent transmittance (photosynthesis lab).

Graphs and Charts:
The failed attempt. The time when each data point was taken is shown by color (photosynthesis lab).
The successful attempt (2nd trial). (On the x-axis, "1.0" refers to the sample of unboiled chloroplasts in darkness. "2.0" refers to the sample of unboiled chloroplasts in light. "3.0" refers to the sample of boiled chloroplasts in light. "4.0" refers to the sample without any chloroplasts). (photosynthesis lab)

Our time intervals for each cuvette  (photosynthesis lab).

Our paper chromatography separating the different pigments (chromatography lab)

Discussion: In the photosynthesis lab we had two trials hence two graphs for our data. As seen above both graphs show different results however one is more accurate than the other due to certain errors and calculations. Going into that we encountered the time for each test being a problem for the first trial as some tests did not meet the time requirements stated in the lab. As such in the 2nd trial we made sure that we had enough time to do all the tests and correctly measure as well the photosynthesis rate. The results of both trials can be contrasted by the scaling of the rate of photosynthesis and also how the 2nd trial showed more of an increase for the unboiled chloroplast in light, which was the one cuvette that should have shown the most progress as time went by. In the first trial it showed a decrease or none at all in the rate of photosynthesis of the 2nd cuvette and that is not suppose to occur. overall our 2nd trial did support what was suppose to happen as the lab stated as we learned to fix the mistakes that affected our results.

Conclusion: We found that there was a wide variety of colors displayed when the chromatography lab was in progress. As the colors showed the solubility of each was shown on the strip of paper. As for the 4b which was the photosynthesis part of the lab, we found out about what went wrong the first time we did the experiment and that was the time for the reaction to occur. Given a time limit when not enough time was given the rate of photosynthesis did not really occur in a situation that was supposed to happen. For example the unboiled chroloplast with light in our first attempt showed no response in the rate of photosynthesis. Hence why a 2nd trial was done to see if there was a huge difference and there was.

References: N/A

1 comment:

  1. Not sure your graph is correct? There should be a line for each cuvette over time not four lines attributed to time? Rf data and calculations? Your discussion should include references to actual data from the experiment.