Mitochondria
Mitochondria Mitochondria, small cellular structures, or organelles, found in the cytoplasm of eukaryotic cells (cells with a nucleus). Mitochondria are responsible for converting nutrients into the energy-yielding molecule adenosine triphosphate (ATP) to fuel the cell's activities. This function, known as aerobic respiration, is the reason mitochondria are frequently referred to as the powerhouse of the cell. Mitochondria are unusual organelles in that they contain deoxyribonucleic acid (DNA), typically found in the cell’s nucleus, and ribosomes, protein-producing organelles abundant in the cytoplasm. Within the mitochondria, the DNA directs the ribosomes to produce proteins, many of which function as enzymes, or biological catalysts, in ATP production. The number of mitochondria in a cell depends on the cell's function. Cells with particularly heavy energy demands, such as muscle cells, have more mitochondria than other cells.