Step four requires you to remove your leaf from the alcohol and to wash it in cold water to remove the alcohol. Now you are ready for step five. Iodine solution should not be inhaled. If it gets in the eyes, it should be washed out immediately and professional advice should be sought. If your leaf contains starch, then the golden-brown iodine solution will become black in color.
Energy is needed to drive the chemical reactions that occur in cells.
Some energy is also used to maintain the internal temperature of the organism. Sugar that is not used for energy is combined with minerals from the soil to make other essential molecules such as proteins. Starch is stored in cells as an energy reserve, but cellulose is a molecule needed by plants to make their cell walls. Cellulose is a raw material for products such as cellophane and rayon, and cotton is almost pure cellulose. In plants such as trees, the spaces between the cellulose molecules in some cell walls become filled with a substance called lignin.