Cells are divided into autotrophic and heterotrophic. Autotrophic green plant cells synthesize nutrients through photosynthesis. Some bacteria synthesize the organic matter they need through chemical energy, which provides energy to synthesize other substances they need, but some raw materials, such as water, carbon dioxide and other inorganic substances, need to be obtained from the outside. Heterotrophic cells cannot be synthesized by photosynthesis or chemical synthesis, but they can be transformed into another nutrient by using ready-made nutrients.