Laboratory Module 8. Plant Physiology (2): Plant Pigment Paper Chromatography
All organisms need energy for their metabolic processes. They also need “food” to produce that energy. Plants are autotrophs (self-feeders). Plants produce their food through a process called Photosynthesis. The food that they produce is the sugar glucose. Animals and other organisms are heterotrophs (other- feeders). They must consume other organisms (plants) in order to eventually get their glucose. Both plants and animals use glucose as an input to the process of Cellular Respiration (another subject) to produce ATP molecules. ATP molecules are the energy source for all metabolic processes.
Log on to the following web site for a good explanation of photosynthesis. Pay attention to the part that discusses chlorophyll and accessory pigments.
The process of photosynthesis utilizes pigments to absorb light to energize the procedure. Through the process of paper chromatography you can separate these pigments to demonstrate a partial step in the photosynthesis process.
Log on to the following web site for an explanation of how these pigments are separated.
Plants contain pigment molecules that are the center of the plants ability to make energy and food from sunlight (photosynthesis). The main pigments are chlorophylls (green), but other pigments of different colors assist in light absorption. This lab allows you to discover what these pigments are and their properties.
Materials: A large bag of spinach leaves. Alcohol Solvent: rubbing alcohol (isopropanol) or grain/everclear (ethanol). Coffee filters. Blender, Juicer or Food Processor Small to medium glass jars w/lids (baby food jars or jam jars). Various, common kitchen utensils.
Setup Time: about 2-3 hours
Procedure: 1. Take the bag of spinach leaves and remove the petioles (the stem like part). 2. Place the leaf blades in a blender, juicer or food processor (a juicer or an old fashioned bender are the best) and liquefy them. 3. Remove the liquid to a jar or container. You may need to squeeze the mixture through cheese cloth or an old tea shirt to strain it properly. 4. Cut the paper filter into strips about 1 inch wide and at least 6 inches long. Draw a pencil line about 1 inch from one edge. This will be the bottom of the chromatography strip. 5. Remove the liquid in small aliquots with a pipette or modified straw1 and lay down a green line just above and parallel to the pencil line. 6. Repeat step # 5 twice more and let dry. 7. Repeat steps #5 & #6 until the green line is very, very, very dark green. (30 – 60 pigment/let dry applications). 8. Attach the paper to the jar, so the green line is on the bottom and the top hangs over the edge of the jar. 9. Add at enough alcohol to the chromatography jar without touching the green line. Loosely attach the lid of the jar & monitor the pigments movements. As the alcohol evaporates, it will separate the different pigments along the paper, according to molecular size and weight, with the largest/heaviest on the bottom. 10. Remove the paper when the pigments travel almost to the top of the jar (20 – 30 minutes?) and allow them to dry thoroughly
Hint: If your chromatogram is hard to see, repeat the experiment and lay down another replicate green line using more liquid/pigment along the line and make sure that it dries thoroughly between treatments.
Write a report on your exercise. It should be 2 pages.
Explain the mechanism for chromatography. Explain how you did your personal exercise.
Include photos of the process. You may use any source of information that is available
Chapter 19 Ethical Dilemma Discussion, “The Wages of Sin?”
Read the “Wages of Sin?” Ethical Dilemma scenario on pages 687-688 of your text and respond to the following Discussion questions below this message:
What Would You Do?
1) Continue Westwind’s zero-tolerance policy toward shoplifting. It’s the right thing to do – and it will pay off in the end in higher profitability because the chain’s reputation for being tough on crime will reduce overall losses from theft.
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