Starch

Starch makes up the nutritive reserves of many plants. During the growing season, the green leaves collect solar energy. In plants with tuberous roots, this energy is transported as a sugar solution down to the tubers, and it is down there, that the sugar is converted to starch in the form of tiny granules occupying most of the cell interior.

The conversion of sugar to starch takes place by means of enzymes. Then, the following spring, enzymes are also responsible for the re-conversion of starch to sugar, which is transported upwards as energy for the growing plant.

Starch is the most common carbohydrate in the human diet and is contained in many staple foods. The major sources of starch intake worldwide are the cereals (rice, wheat, and maize) and the root vegetables (potatoes and cassava).