Photosynthesis Lab
Photosynthesis Lab
Discussion: Photosynthesis is the process whereby food is made from simple inorganic substances. The equation for Photosynthesis is: Carbon Dioxide + Water to give you Oxygen and Glucose. The boiling point of ethanol is 78o Celsius. Leaves are adapted to carry out photosynthesis in a number of ways. They are generally broad and flat with a large surface area to absorb a lot of light and carbon dioxide. They lie at 900 to the sunlight and are spaced around the stem to catch as much light as possible. A waxy cuticle prevents water loss from both surfaces of the leaf, and is transparent to let light through. The leaf was boiled with the ethanol to remove the wax which may hinder the testing for starch. Boiling the leaf killed the cells and teared open the cell membranes so the iodine stain easily entered the cells. The ethanol was also used to remove chlorophyll which is why the ethanol eventually turned green. The leaf turned bluish-black when the iodine was dropped. This means starch was present. The reaction between the iodine and starch is what produces the bluish-black colour. Iodine was poured on another waxy leaf and there was no reaction. Starch is a long-branched polysaccharide, composed exclusively of glucose units, that is the primary storage carbohydrate in plant cells.
Precaution: Handle the hot apparatus and material with care. Do not heat the tube directly with a Bunsen flame.
Conclusion: Starch was present in the waxy green leaf.
Discussion: Photosynthesis is the process whereby food is made from simple inorganic substances. The equation for Photosynthesis is: Carbon Dioxide + Water to give you Oxygen and Glucose. The boiling point of ethanol is 78o Celsius. Leaves are adapted to carry out photosynthesis in a number of ways. They are generally broad and flat with a large surface area to absorb a lot of light and carbon dioxide. They lie at 900 to the sunlight and are spaced around the stem to catch as much light as possible. A waxy cuticle prevents water loss from both surfaces of the leaf, and is transparent to let light through. The leaf was boiled with the ethanol to remove the wax which may hinder the testing for starch. Boiling the leaf killed the cells and teared open the cell membranes so the iodine stain easily entered the cells. The ethanol was also used to remove chlorophyll which is why the ethanol eventually turned green. The leaf turned bluish-black when the iodine was dropped. This means starch was present. The reaction between the iodine and starch is what produces the bluish-black colour. Iodine was poured on another waxy leaf and there was no reaction. Starch is a long-branched polysaccharide, composed exclusively of glucose units, that is the primary storage carbohydrate in plant cells.
Precaution: Handle the hot apparatus and material with care. Do not heat the tube directly with a Bunsen flame.
Conclusion: Starch was present in the waxy green leaf.