ChromatographyChromatography

Plant Pigment InvestigationPlant Pigment Investigation

Lab 4: Plant Pigments Lab 4: Plant Pigments and Photosynthesisand Photosynthesis

Overview:Overview: In this laboratory students will separate In this laboratory students will separate

plant pigments using chromatography.plant pigments using chromatography.

Chromatography-separating and Chromatography-separating and identifying pigments and other molecules identifying pigments and other molecules from cell extracts that contain a complex from cell extracts that contain a complex mixture of molecules.mixture of molecules.

Plant Chromatography Plant Chromatography Pre- LabPre- Lab

Before doing this laboratory students Before doing this laboratory students should understand:should understand:

how chromatography separates two or how chromatography separates two or more compounds that are initially present more compounds that are initially present in a mixture;in a mixture;

the process of photosynthesis;the process of photosynthesis; the function of plant pigments;the function of plant pigments;

Plant Pigment Plant Pigment Chromatography ProcessChromatography Process

The solvent moves up the paper by capillary action, The solvent moves up the paper by capillary action, which occurs as a result of the attraction of solvent which occurs as a result of the attraction of solvent molecules to the paper and the attraction of solvent molecules to the paper and the attraction of solvent molecules to one another.molecules to one another.

As the solvent moves up the paper, it carries along any As the solvent moves up the paper, it carries along any substances dissolved in it. substances dissolved in it.

The pigments are carried along at different rates The pigments are carried along at different rates because they are not equally soluble in the solvent and because they are not equally soluble in the solvent and because they are attracted, to different degrees, to the because they are attracted, to different degrees, to the fibers in the paper through the formation of fibers in the paper through the formation of intermolecular bonds, such as hydrogen bonds.intermolecular bonds, such as hydrogen bonds.

Chromatography SampleChromatography Sample

Plant PigmentsPlant Pigments

Beta carotene (yellow/orange)-is carried along near the Beta carotene (yellow/orange)-is carried along near the solvent front because it is very soluble in the solvent solvent front because it is very soluble in the solvent being used and because it forms no hydrogen bonds being used and because it forms no hydrogen bonds with cellulose. with cellulose.

Xanthophylls (yellow/brown)-found further from the Xanthophylls (yellow/brown)-found further from the solvent front because it is less soluble in the solvent solvent front because it is less soluble in the solvent and has been slowed down by hydrogen bonding to the and has been slowed down by hydrogen bonding to the cellulose. cellulose.

Chlorophylls-bound more tightly to the paper than are Chlorophylls-bound more tightly to the paper than are the other pigments. (a-yellow/green, b-blue/green)the other pigments. (a-yellow/green, b-blue/green)

Plant Chromatography Plant Chromatography Photosynthesis Post-LabPhotosynthesis Post-Lab

After doing this laboratory students should After doing this laboratory students should be able to:be able to:

separate pigments and calculate their Rf separate pigments and calculate their Rf valuesvalues