A compound needed for the proper functioning of an enzyme, a protein that speeds up the rate at which chemical reactions take place in the body. Coenzyme Q10 is used to produce energy to fuel cell growth and maintenance. Coenzyme Q10 is thought to improve the function of mitochondria, the "powerhouses" that produce energy in cells. Coenzyme Q10 is also an antioxidant, a substance that protects cells from highly reactive chemicals called free radicals that can damage cells and their DNA. The highest amounts of coenzyme Q10 are in the heart, liver, kidneys, and pancreas and the lowest amounts are in the lungs. The levels of coenzyme Q10 normally decline with age.