Sugar is one of the sources of energy for cells.
The sugar called glucose is made during the process of photosynthesis within the chloroplasts of plant cells. The chlorophyll (a green pigment) within the chloroplasts captures sunlight energy. This energy is used to transform carbon dioxide and water into glucose molecules and oxygen gas. The glucose that is created via photosynthesis is then used by the plant as energy to power the cells, or stored. It is also used by consumers (also known as heterotrophs), which are organisms that must eat other things for food. The mitochondria of plant and animal cells combine the glucose with oxygen in order to make (produce) carbon dioxide, water, and a form of energy known as ATP. This process is known as cellular respiration. Note that photosynthesis and cellular respiration are opposites of one another. This phenomenon is an example of the interrelationships of all living things.