What is the powerhouse of the cell, responsible for producing energy?

The mitochondria are often called the 'powerhouse of the cell' because they produce most of the cell's energy in the form of ATP through cellular respiration. The nucleus contains the cell's DNA and controls its activities; ribosomes build proteins; and the cell membrane controls what enters and leaves the cell. Knowing the main organelles and their functions is core General Science content. Mitochondria convert nutrients and oxygen into usable energy, which is why cells with high energy needs (like muscle cells) contain many of them.