Mitochondria are known as the powerhouses of the cell. They are organelles that act like a digestive system which takes in nutrients, breaks them down, and creates energy rich molecules for the cell. In cellular respiration sugar with the help of oxygen is broken down into ATP. In eucaryotes these reactions all take place in mitochondria, the organelle to which pyruvate and fatty acids are directed for acetyl CoA production. Therefore not be surprised to discover that the mitochondrion is the place where most of the ATP is produced in animal cells. The endoplasmic reticulumcan either be smooth or rough, and in general its function is to produce proteins for the rest of the cell to function. The rough endoplasmic reticulum has on it ribosomes, which are small, round organelles whose function it is to make those proteins