These are membrane bound organelle which liberates energy. They are known as power houses. ATP is the most common form of liberation of energy. They have their own DNA. They constitute nearly one fifth of total volume of cell. It has folded membrane known as cristae. Folded membrane provides large surface area for production of more energy.
It has two membrane systems. Outer membrane is made of phospholipids and proteins which accounts for their atomic weight. Inner layer is very permeable. Mitochondria have some specific role for some organs. In liver they help to process cellular waste product.
They are maternal in origin and have around three thousand proteins. As ageing occurs mitochondria starts degenerating. They play a vital role in ageing. A new research of removing DNA from mitochondria to halt ageing has been going on. Mitochondria are peculiar feature of eukaryotic organisms and are absent in prokaryotic organism.