The mitochondria are often referred to as the powerhouse of the cell. The reason for this is because it is their job to take in nutrients, break them down and convert them into useable energy for the cell. This conversion of energy is a process known as cellular respiration. Mitochondria are rod shaped organelles found in the cytoplasm of cells. The mitochondria is a relatively small organelle but because it has a large surface area inside due to many folds it can produce a large amount of energy for the cell.