Aspen Institute. The Aspen Institute is an international nonprofit organization founded in 1950 as the Aspen Institute of Humanistic Studies. The organization is dedicated to fostering enlightened leadership, the appreciation of timeless ideas and values, and open-minded dialogue on contemporary issues.
Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins), in the nucleic acids (DNA and RNA) and in the energy transfer molecule adenosine triphosphate. The human body contains about 3% by mass of nitrogen, the fourth most abundant element in the body after oxygen, carbon, and hydrogen.
Four important classes of organic moleculesâcarbohydrates, lipids, proteins, and nucleic acidsâare discussed in the following sections. Carbohydrates. Carbohydrates are classified into three groups according to the number of sugar (or saccharide) molecules present: A monosaccharide is the simplest kind of carbohydrate.