Definition and purpose Amino acids are organic compounds made of carbon, hydrogen, oxygen, nitrogen, and (in some cases) sulfur bonded in characteristic formations. Strings of amino acids make up proteins, of which there are countless varieties. Of the 20 amino acids required for manufacturing the proteins the human body needs, the body itself produces only 12, meaning that we have to meet our requirements for the other eight through nutrition. This is just one example of the importance of amino acids in the functioning of life. Another cautionary illustration of amino acids' power is the gamut of diseases (most notably, sickle cell anemia) that impair or claim the lives of those whose amino acids are out of sequence or malfunctioning. Once used in dating objects from the distant past, amino acids have existed on Earth for at least three billion years—long before the appearance of the first true organisms. Amino acids build proteins, and proteins are life-sustaining macronutrients. Yet simply calling amino acids the building blocks of protein doesn’t do justice to their value. While some amino acids only make proteins, others fill a variety of roles, from supporting metabolism to protecting your heart. Your body can also use amino acids for energy when you lack carbs and fats.