Teachers' Notes - Meet the algae: diversity, biology and energy

Algae Chromatography

The aim of the exercise is to show the diversity of algae, and to demonstrate that red algae also contain green pigments (the green chlorophyll) and photosynthesise. This experiment was developed in conjunction with the researchers at the University of Cambridge, who are part of the Meet the algae: diversity, biology and energy exhibit team.

Materials required

• Safety glasses
• Centrifuge
• Green algae culture
• Red algae culture
• Small mortar and pestle
• 1 cm³ plastic pipettes
• Centrifuge tubes (or test-tubes if you don’t have access to a centrifuge)
• Whatman 3MM paper (Cut into strips for the students)
• Ethanol (Highly flammable, Harmful; see CLEAPSS Hazcard 40A)
• Fine paint brushes
• 50cm³ beaker

Prepare two stocks of algae: a red algae (Porphyridium) and a green algae (Chlorella). You can get the red algae Porphyridium purpureum, other red algae, and the green Chlorella from www.Sciento.co.uk. Euglena is another green-coloured alga you can use.

By extracting the pigments, and then analysing them using chromatography, it is possible to demonstrate that the red algae also contain green pigment, which is usually masked by their red pigment.

Safety: Eye protection must be worn. A risk assessment must be done for this activity. Ethanol is highly flammable, therefore must be no naked flames and wash your hands afterwards.

Results

The green spot moves up the paper, displaying no further colours. The red spot becomes bright red and green pigments move up the paper.

The green algae contain chlorophyll a and chlorophyll b (green pigments). The red algae contain chlorophyll a and phycobilin (a red pigment). Although chlorophyll is the major pigment for photosynthesis, the other pigments help algae harvest light of different wavelengths, which is useful when they are deeper in water.

You should point out to your students that algae are simple (lower) plants. It is also worth mentioning that all land plants originated from one group of green algae.

Answers

• 1. Some algae can swim and react to light (which is known as phototaxis), so in order to settle they need to be kept in the dark.
• 2. Both the green and red algae contain green pigment – the students should be able to see this as the pigment moves up the blotting paper.  
• 3. This green pigment is chlorophyll which is vital for photosynthesis and allows the algae to obtain energy from sunlight.
• 4. The other pigments help algae harvest light of different wavelengths such as when they are deeper in water, giving them a greater chance of survival.

Curriculum links

Organisms and health

• 5a: Organisms are interdependent and adapted to their environment.
• 5b: Variation within species can lead to evolutionary changes, and similarities and differences between species can be measured and classified.

Energy, electricity and radiations

• 7b: Electrical power is readily transferred and controlled, and can be used in a range of different situations.

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