16 6 Macroalgae and microalgae are photosynthetic organisms. Seaweeds are macroalgae that live attached to rock in coastal areas. Some seaweeds are green, some are brown and some are red. The colour of seaweeds depends on the photosynthetic pigments contained in their cells. Green seaweeds contain chlorophyll, brown seaweeds contain chlorophyll and fucoxanthin and red seaweeds contain chlorophyll and phycoerythrin. (a) (i) Explain why these seaweeds have different absorption spectra and action spectra. 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Turn over 17 (ii) The diagram shows the position that these seaweeds occupy on submerged rock and the depth to which different wavelengths of light penetrate into the water. green seaweed brown seaweed red seaweed water level red light green light blue light submerged rock Explain why the seaweeds occupy different positions on the submerged rock. 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Fucoxanthin has anti-inflammatory, anti-tumour, anti-diabetes, anti-malarial and anti-obesity activity in humans. The diagram outlines the steps taken to extract fucoxanthin from microalgae. Cells of microalgae grown in a culture in a laboratory Cells washed Fucoxanthin extracted The table shows three methods used for washing the cells and extracting the fucoxanthin. Method Liquid used for washing cells Chemical used to extract fucoxanthin A water ethanol B culture media ethanol C culture media water Turn over 19 The graph shows the mass of fucoxanthin extracted from 1 dm3 of cell culture. 90 80 70 60 50 40 30 20 10 0 Mass of fucoxanthin / mg A B C Method (i) Calculate how many times more fucoxanthin was extracted using method A compared with method B. (1) Answer ................................................................ (ii) Explain why different masses of fucoxanthin were extracted using these three methods. 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(Total for Question 6 = 10 marks)