Science for you to try - Meet the algae: diversity, biology and energy

Algae Chromatography

Algae are a diverse range of aquatic organisms that include seaweeds and green slime in ponds.

In this experiment you will be looking at the different pigments that are present in two algae – a red alga (Porphyridium, left) and a green alga (Chlorella, right).

Procedure

You will need:

• Centrifuge
• Green algae culture
• Red algae culture
• Small mortar and pestle
• 1 cm³ plastic pipettes
• Centrifuge or test-tubes
• Strips of blotting paper
• Ethanol
• 50 cm³ beaker
• Fine paint brushes

Safety: Wear safety glasses.

1. Centrifuge 10 cm³ of culture in a centrifuge tube to form an algae pellet. If you do not have a centrifuge, put the algae mixture in a small test-tube in the dark and allow to settle. This should take around one hour.

2. Carefully pour off the liquid, trying to avoid disturbing the pellet of algae cells at the bottom. Then place the tube containing the algae pellet in a freezer overnight.

3. Grind the pellet in a small mortar and pestle and re-suspend the ground pellet in a small amount of water using a 1 cm³ plastic pipette. Start off with 1-2 drops and add more if necessary, but try to use the minimum so that the solution is as concentrated as possible.

4. Draw a line in pencil about 2 cm from the bottom of the paper you’ve been given. Use a fine paintbrush to place small dots of samples of green Chlorella and red Porphyridium next to each other. Add the samples a little at a time leaving them to dry in between.

5. Place the paper in 5 cm³ of ethanol (Note: make sure the solvent level is not above the level of the pencil line) in a 50 cm³ beaker and cover with a watch glass. Leave for around 10 mins to allow the solvent to move up the paper. What do you observe?

Questions

• 1. Why is it best to let the algae settle in the dark?
• 2. Where can you see the green pigment?
• 3. What do you think this green pigment contains?
• 4. Why do you think some algae contain more than one pigment?
   

Instructions for Teachers

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