Here's why:

* Double Membrane: Mitochondria have two membranes - an outer membrane and an inner membrane. The inner membrane is highly folded into cristae, which increase its surface area.

* Inner Folded Contains its own DNA: The inner membrane encloses the mitochondrial matrix, which contains its own circular DNA molecule. This DNA is separate from the cell's nuclear DNA and codes for some of the proteins involved in mitochondrial function.

Key Functions of Mitochondria:

* Cellular Respiration: They are responsible for the production of ATP (adenosine triphosphate), the cell's primary energy source.

* Cellular Metabolism: They play a role in various metabolic processes, including the synthesis of amino acids and fatty acids.

* Apoptosis: They are involved in programmed cell death.

Let me know if you have any other questions!