Read the small print on the side of the box! If you read the second and third lists of ingredients, you will see that they have listed 3 enzymes in the washing powder: amylase, cellulose and protease. For example, protease digests protein. Suppose you spill egg onto your clothes. The protease would digest the protein in the egg stain making it much easier to wash out. Biological washing powder contains enzymes. Enzymes are biological catalysts. In other words, they speed up reactions without being used up themselves. They do their work by a lock and key mechanism. Molecules of the correct shape fit into active sites on the side of the enzyme. Then they can react more easily because fitting into the enzyme reduces the amount of energy needed for a reaction to happen (this is called the activation energy). Enzymes are made of protein. If you overheat them, you destroy the special shape of the active sites. We say that the enzyme has been denatured. So you mustn't let the washing water get too hot. Biological washing powders work faster than ordinary powders at lower temperatures. At cold temperatures even enzymes work slower because the molecules that are going to react (called the substrate) have less kinetic energy and are moving around more slowly. The slower they move, the less frequently they collide with other molecules, so fewer reactions happen. Also there is less energy in the collisions so even if they do collide they may not have enough energy to react. Biological washing powders have gone out of fashion because they are often blamed for skin irritation.
