The cell is an energy conversion machine.
Cells absorb, convert, and use several forms of energy in their life processes.
Animals and other non-photosynthetic organisms directly or indirectly utilise food produced by plants. All cells, green and non-green, use food energy in their life processes. The energy-related organelles, chloroplasts and mitochondria, are transformers, changing one form of energy into another. While chloroplasts are unique to plant cells, mitochondria are found in both plant cells and animal cells. Chloroplasts carry on photosynthesis, during which light energy is used to produce food molecules like glucose.