Plant Pigments & Photosynthesis

                   Plant Pigments & Photosynthesis


In this lab, our lab group separated plant pigments via chromatography and measured the rate of photosynthesis in chloroplasts. We also measured the percent transmittance within chloroplast and DPID solutions. Much went on and this is by far one of our biggest labs. IT all starts with the spinach! Enjoy!


               Part A: Plant Pigment Chromatography

     Before we could start experimenting, we had to make chromatography paper. We did this by cutting out a slip of paper around 6 in long, and then cut the tips on the bottom to make it pointy, like in the picture below. 

        After this, we drew a line around 1.5 cm from the bottom. This will be our pigment origin, which is where we will rub the spinach cells onto. 

        This next part was the fun one. We took a spinach leaf and started crushing it with a coin. We then put the spinach guts onto the pigment origin line we made earlier.

        Once our chromatography paper was ready to go, we hooked it to a cork then placed it into a flask filled with 1 ml of the solvent.We made sure that when the chromatography paper was in the cylinder, the solvent was not touching the pigment. When he solvent was about 1 cm from the top of the paper, we removed the paper from the flask and marked the solvent front.  In this trial, we found 5 bands. We then measured the distance from the pigment origin to each band. 

Analysis: After looking at the results, we concluded that there are many factors that went into how the chromatography paper was separating the pigments. It mainly depended on how soluble each pigment was with the solution that we used as the solvent. That is why there are different bands and some of are different color. They could only go as far as their solubility with the solvent. Ones that were less soluble were farther away from the solvent front. Also, if we had used a different solution as the solvent, the results may have been much different. For the different solvent could be more or less soluble with the different pigments found in the spinach.

                        Part B: Photosynthesis/The Light Reaction

This chart shows what needed to be in the specific solution.

           In this section we filled 5 different cuvettes according to the chart above.  3 out of the 5 cuvettes called for light, so during the duration of the experiment they were placed in front of the incubator. . By placing the cuvettes in the Lab Pro contraption after 5, 10, and 15 minutes we were able to find the % transmittance in each different cuvette. What seemed to of happened is that for the cuvettes that had living chloroplast in them, the longer we let them absorb light the lower the % transmittance got. What seems to be going on here is the living chloroplast  use this light to preform photosynthesis, which gives off ATP which makes the solution more absorbent. The other cuvettes, were supposed to be out control. One was covered in tin foil when left in front of the incubator, and the other had boiled (dead) chloroplasts in the solution.

Analysis: We looked at our results and concluded many observations. The boiled chloroplast solution did not have that much of a change in percent transmittance because there was no reaction going on, thus keeping the solution staying the same. This also follows for the cuvette solutions that were covered in tin foil. They did not have much of a change in percent transmittance because they were not given light to react.

BUT WAIT THERE IS MORE!

So, we decided to take on the Extra Credit challenge, not entirely sure what question(s) we were suppose to answer but here is our explanation on why the spinach glows red under the light and how we got it to glow.

So, our materials consisted of:

Test tube, leaf of spinach, alcohol, light, scissors, beaker and filter paper

First, we cut the leaf of spinach in little pieces and placed it in the beaker. After, we poured a bit of alcohol into the beaker and let it sit for a couple of minutes. Next, we filtered out the pieces of spinach into a clean test tube. At this point, we were only left with the liquid consisting of alcohol and chlorophyll. Lastly, we shined the light at the liquid and saw that it was glowing red!

The point of this was to extract the chlorophyll, next is why it glows red.

Spinach soaking in chlorophyll

So, chlorophyll absorb light and that is how they derive their food source. Chlorophyll is able to absorb different colors of light as well. 

Since the light that is shining gives off a blue light, the chlorophyll absorbs this and it excites the electrons A LOT! Naturally, chlorophyll is not able 

to stay at this high excited state and the electron falls very quickly, giving off the red "glow" as it moves into a new state of being less excited.

WOAH GREEN TO RED!

The solution of alcohol and chlorophyll

C-C-C-CONCLUSION

There is a lot to take in with this whole lab. We applied our knowledge about electrons, absorbency, transmittance, incubation, and chromatography to chlorophyll and chloroplasts. As a group, we were able to discuss and determine all that went on chemically and physically with our lab. Since this lab was so big, we decided to break up the analysis discussion questions at the end of each part of this lab. So in case you missed it, all of our wonderful work and deduction is above! 

Definitely more labs will be posted in the future. with CoolerThanAbsoluteZero's blog.