The smallest units of organic compounds. Important examples of these molecules are based on chains of carbon atoms and come in four major categories: proteins, carbohydrates, lipids, and nucleic acids (DNA and RNA).
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.