* Mitochondria are the powerhouses of the cell, responsible for producing ATP (adenosine triphosphate), the primary energy source for cellular processes.

* Lysosomes are the cellular garbage disposals, breaking down waste materials and cellular debris.

* Ribosomes are the protein factories, responsible for translating genetic code into proteins.

* Golgi complexes are responsible for modifying, packaging, and transporting proteins and lipids.

While all of these structures are important in animal cells, mitochondria are the primary site of energy production.