The mitochondria is an oval/rod shaped organelle surrounded by two membranes, the outer membrane is semi-permeable and lets in small molecules; the inner membrane folds to form cristae (the major site for ATP production, O2 utilisation and CO2 production) and is impermeable meaning substances need to have special protein transportation to enter; and the fluid filled inner space is called the matrix which contains many enzymes that break up sugars such as carbohydrates or glucose. A special characteristic about the Mitochondria is that it contains its own DNA (mtDNA that is passed down from the mother) biologists believe that this has occurred due to phenomena called symbiosis. The main role that the mitochondrion plays is that in aerobic respiration and the production of ATP(adenosine triphosphate).
Aerobic Respiration (simple)
Basically Glucose is broken down into 2ATP, Pyruvate and Water in the first stage of aerobic respiration in the cytoplasm. In the second stage which occurs in the mitochondria, the pyruvate is broken down in the enzyme filled matrix to produce 36ATP, Water and Carbon dioxide.
Just as a mitochondria breaks down pyruvate to provide energy for the cell, emergency generators in an airport combust petrol to produce energy in the form of electricity. Both the mitochondria and the Emergency generator provide their cell or airport with the energy they need to complete their daily functions.