Fig. 1 shows a variegated leaf from a garden plant after it had been kept in light for six hours. A student removed the leaf, boiled it in water, heated it ...
Question 1 Report
Fig. 1 shows a variegated leaf from a garden plant after it had been kept in light for six hours. A student removed the leaf, boiled it in water, heated it in ethanol in a water bath, rinsed it, and added iodine solution. Only the green areas turned blue-black. The student used this test to investigate where food is made in the leaf.
(a) Name the green pigment needed for photosynthesis. [1]
(b) Explain why the leaf was boiled in water before it was placed in ethanol. [2]
(c) State the colour shown by an area containing starch after iodine solution is added. [1]
(d) Explain what the result shows about the green parts of the leaf. [1]
Answer Details
(a) The green pigment needed for photosynthesis is chlorophyll. [1]
(b) Boiling the leaf in water kills it and stops chemical reactions. It also makes cell membranes permeable so iodine can enter the cells, or removes the waxy cuticle barrier. [2]
(c) An area containing starch turns blue-black when iodine solution is added. [1]
(d) Only green areas became blue-black, showing that starch was made only in green areas. Therefore chlorophyll is needed for photosynthesis. [1]
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