Plant Pigments and Photosynthesis

Lab 1

Purpose: The purpose of this lab was to be able to see the many different pigments that make up the leaves colors. This would provide us with an explanation of why the leaves change colors in the fall. 

Introduction: Chromatography is used to separate the pigments of the leave. The paper allows the different pigments to grab onto the paper and begin to spread at different speeds causing them to separate. This allows us to observe which pigment moved up the farthest and also to see all the pigments that go into the color of a leaf. 

Methods: For this experiment, we put 1 cm of solvent in the bottom of a graduated cylinder. We then took a piece of filter paper, cut it to a point, and used a coin to rub some of a spinach leaf onto the paper. We then submerged the tip of the filter paper in the solvent, allowing it to move up the paper and carry the pigment with it. When it was near the top, the filter paper was removed and the location of each band of pigment was marked.

Data:

Distance from the solvent line.

The paper used and next to a ruler

Discussion: The first time we did this expirement we didn't add enough pigment, so the lines were not visible. The second time we did and the pigments went up the paper. Chlorophyll B was the one that went up the lowest with 33 millimeters from the point. Xanthophyll was next with 43 millimeters from the point. Chlorophyll A was the third from the point which was 72 millimeters. The fourth was beta carotene with 129 millimeters. We could have added more pigment for better results and brighter more defined lines.

Conclusion: This lab demonstrated that there are many pigments involved in gathering energy from the sun. The different locations on of these pigments on the filter paper demonstrated the varying amount of these pigments, as well as the relative solubility of each. 

References:      http://www.howstuffworks.com/chromatography-info.htm 

Lab 2:

Purpose: The purpose of this lab was to see the effects of DPIP, boiled or unboiled, and amount of light on the percent transmittance using a spectrophotometer. Our control group was cuvette one because it contained no DPIP, unboiled chloroplasts and was exposed to light. The other 4 were our experimental groups. 

Introduction: Spectrophotometers are used to measure the percent of transmittance from a solution placed in the machine. Transmittance is the amount of light that makes it through the solution. Absorption is how much of the light is absorbed by the solution.  Spectrophotometers use a light source that is shined through the solution and on the other side is a sensor that measures how much is transmitted through the solution and how much is absorbed.

Methods: We first added distiller water to a phosphate buffer, this was in all of the test tubes for all five solutions. Then we added DPIP and boiled or unboiled chloroplast to the test tubes. Then we filled the cuvettes three quarters of the way full and put it in the colorimeter. We put the cuvettes behind a light for five, ten and fifteen minutes. We took the readings of how much light was transmitted through.

The amount of each item we needed to put in each test tube.

The lest up we used for to have light in the cuvettes.

Data:

Graphs and Charts: 

Discussion: Only the graph of our 2nd attempt is pictured above. In our first attempt, we got very strange and inconsistent data, but using double the DPIP for our 2nd attempt corrected the problem.  Looking at our graph, it can easily be observed that cuvettes 3 had the highest transmission. This is almost certainly because it most closely mimicked natural photosynthetic conditions. The chloroplasts were unboiled and therefore not  denatured, and there was light shining on it. This allowed the electrons in photosystems I and II to be excited, beginning photosynthesis and eventually processing DPIP, turning the solution from blue to clear and allowing for a higher transmittance. On the other hand, all the other cuvettes showed a much lower transmittance rate, because in each case the chloroplasts were either boiled, starved of light, or both, preventing photosynthesis from starting and therefore causing DPIP to remain unprocessed and the solution to remain blue. 

Conclusion: The lab shows that transmition of light through the solution is best in conditions that are like the natural conditions of  a plant. DPIP is processed when there is light and unboiled choloroplast. Light and non denatured chloroplasts are essentual for photosynthesis to occur, so seeing that the solution that was most like natural photosynthetic conditions had the most light transmittance, meaning it was most effective at photosynthesis. 

References:

Lab 4 Plant Pigments and Photosynthesis

 http://simple.wikipedia.org/wiki/Spectrophotometer

http://www.biologyjunction.com/lab_4_plant_pigments.htm