PLANT PIGMENTS AND PHOTOSYNTHESIS LAB

October 23, 2017

Purpose To use the process of chromatography, in order to indicate the pigments that lie in a green and non-green colored leaf, and measure the Rf value of each pigment. 

Background Photosynthesis is the process in which plants convert light energy into chemical energy. During most times of the year, leaves contain more chlorophyll than any other pigment. When fall comes around and chlorophyll pigment begins to break down, the other pigments begin to appear in the leaves, which is why we notice more reds and oranges in the leaves. Chromatography, allows us to see the pigments which lie in the leaves. 

Hypothesis If a leaf is smudged on a piece of chromatography paper, and placed in alcohol, then the pigments of the green and non-green plant will travel up the paper and separate based on color.  

Data

Green Plant Pigment 

Solute Color	D solvent (cm)	D unknown (cm)	Rf=D unknown/D solvent
Yellow	2.7	3.3	0.82
Green	3	3.3	0.91

Non-green Plant Pigments

Solute Color	D solvent (cm)	D unknown (cm)	Rf=D unknown/D solvent
Purple	0	3.2	0
Green	2.7	3.2	0.84

Questions

1. Chromatography is a method used in separation of a mixture of compounds into its individual components. Chromatography is especially important when one wants to analyze the molecules, pigments, or components of a mixture. 
2. There are a few factors which impact the separation of the mixture. Factors that impact the separation of the mixture are the molecular size of the solutes, the solubility of the solute in the solvent, and the attraction to the chromatography paper. Because of their different characteristics, each molecule travels at a different speed when pulled along the piece of paper towelling by the solvent. The lighter particles move more quickly and a greater distance than the heavier particles. 
3. The chromatography paper absorbs the substance and creates a visual for the viewer to witness the pigments or separation of the mixture. 
4. The type of solvent either allows the pigment to move, or not move up the chromatography paper. 
5. The retention value, or Rf value for short, is defined as the ratio of the distance moved by the solute over the distance moved by the solvent. It tells us how far the unknown pigment traveled in relation to the distance the solvent traveled.
6. The Rf value is useful for scientists because it allows scientists to identify the pigment by comparing its Rf value to that of a known standard.
7. D(unknown) signifies the distance the solute travelled.
8. D(solvent) signifies the distance the solvent travelled.
9. From the green leaf chromatogram, I was able to identify the pigments green and yellow.  
10. From the non-green chromatogram, I was able to identify the pigments purple and green. 
11. From this experiment, I found out that leaves contain not just chlorophyll, but accessory pigments known as carotin (orange), xanthophyll (yellow), and anthocyanin (red).
12. Why didn’t my group and I notice any of the other pigments that are in leaves, like carotene and anthocyanin through the chromatography experiment?

       Non-Green Leaf, Green Leaf, Black Ink Marker