1) Cells trap energy from food through metabolism and change it into forms that can be used to sustain life. Producers, like plants, can make their own food through photosynthesis while consumers rely on producers or other consumers for food. 2) Photosynthesis uses energy from sunlight to convert carbon dioxide and water into oxygen and sugars like glucose in plants. This occurs through a series of steps in the chloroplasts. 3) Cellular respiration releases energy stored in food molecules and is used by both producers and consumers. It breaks down glucose and other foods within mitochondria to produce carbon dioxide, water, and energy.