Living organisms obtain energy from nutrients through various metabolic processes, primarily cellular respiration. This process involves breaking down complex organic molecules, such as carbohydrates, proteins, and fats, into simpler molecules to release stored energy. In animals, this usually leads to the production of ATP (adenosine triphosphate), which serves as the energy currency of the cell. Additionally, photosynthetic organisms, like plants, convert light energy into chemical energy by synthesizing glucose from carbon dioxide and water. This energy is then used for growth, reproduction, and maintenance of cellular functions.