Food molecules—carbohydrates (sugars and starch), fats, and proteins—contain many chemical bonds, each representing a small package of stored energy. When foods are used in the biochemistry of cells, the bonds are broken and energy is released—energy to construct other molecules, such as cellulose and lignin needed for growth, to make chromosomes dance through cycle after cycle of mitosis, to transport food in the phloem, to regulate membrane permeability, and to power countless other functions.
