The storage batteries of the cells is

These are cylindrical or filamentous structures found in all aerobic eukaryotic cells except the mature and old mammalian RBCs. Each mitochondrion is a double membrane bound structure enclosing a dense fluid called matrix. The inner membrane is folded inwards to form cristae which increase the surface area. The matrix contains proteins, lipids, few ribosomes, enzymes and DNA. The cristae bear numerous stalked particles called the oxysomes. Mitochondria provide site for cellular respiration resulting in the formation of energy. Hence they are termed as the storage batteries of the cells.