Photosynthetic Pigment Lab Report: Photosynthetic Pigments

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Linh Dinh; Omar Cherif; Alexandra Olsson IB2G/IB2B
Dr. Young
Photosynthetic Pigments Lab Report
December 1, 2014

Photosynthetic Pigments Lab
The aim of this lab is to separate photosynthetic pigments by chromatography, a method used to separate the components of a mixture, and to measure each pigment’s Rf value.

There are different types of chromatography, and the one which this lab focuses on is paper chromatography. The components of the mixture, in this case, spinach leaves mixed with acetone, are pipetted at one end of the chromatography paper and hung in a jar slightly above solvent vapor to create the reaction.

Hypothesis
For this lab, we expect the polar pigments will have the largest Rf value whereas the non-polar pigments will
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B-carotene was the pigment which had the largest Rf value, and it is a pigment which is insoluble in water and petroleum ethel. Chlorophyll B on the other hand had the least Rf value and is, also insoluble in water, but very soluble in petroleum ether. Based on these results, we can deduce that those pigments with high Rf values are insoluble in the solvent, and as the Rf value decrease, the pigments become more soluble in the solvent. This order would be opposite if the solvent were to be replaced with water rather than the nonpolar solvent mixture of petroleum ether and acetone because of the polarity patterns.

Chlorophyll A and B are both insoluble in water but both very soluble in the solvent made up of petroleum ether and acetone. The tail of both molecules is made up of carbon atoms, and the head is hydrophilic; the one difference between the A and B molecules is on the head of the A molecule, CH3 is present, whereas on the B pigment, a carbon atom is double bonded to an oxygen atom and single bonded to a hydrogen atom. From this, we can speculate that the hydrophilic properties of Chlorophyll make the two pigments very soluble in the solvent. They are insoluble in water based on the fact that the entire molecule is not
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The wavelength of the absorption maximum for the chlorophylls are red and blue. The wavelengths of absorption maximum for the other three carotenoids is blue-green. Shown in the graph below.

The reason why plants have more than one or more pigments is because chlorophyll has a small range of light that it captures. So it needs to pair up with other pigments that captures the wavelengths of light that chlorophyll misses especially the blue spectra and another function of these other pigments is to protect the leave from UV damage, an example for this kind of pigment is Xanthophyll. The reason why plant leaves are green is because the leave absorbs all the wavelengths of light except the green ones and the reflection of green is what we

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