What Do Plants DO with the Sugar They Make?
All living things need a source of energy, and for plants, the sugar made in photosynthesis (using the energy of photons) is that source. 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. Sugar molecules can also be joined together to make two important large molecule carbohydrates: starch and cellulose. 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. It is this lignification of the cellulose of cell walls that produces the wood of trees. So sugar is the ener
