What Are the Four Families of Small Organic Molecules That Are Used to Build Big Molecules?

Four different types of small organic molecules combine to form larger, more complex molecules. Each of these families has its own roles to play in building bodies, regulating metabolism, providing energy and forming cells. Each type of small molecule joins with similar ones to form the larger molecules, and the combinations of larger molecules form all the animals and plants on the planet.

  1. Carbohydrates

    • Carbohydrates include breads and potatoes.
      Carbohydrates include breads and potatoes.

      Carbohydrates provide quick energy. Small organic molecules of carbohydrates combine to form larger carbohydrate molecules. Many of the foods containing carbohydrates may seem familiar to you: breads, potatoes, corn and rice. The most common organic molecule is cellulose, which is a carbohydrate. Cellulose makes up wood and all plant bodies. In addition to cellulose, sugars and starches round out the carbohydrate family. These are vital energy sources for all animals.


    • The membranes that keep cells separate are built from lipids.
      The membranes that keep cells separate are built from lipids.

      Lipids offer long-term energy, along with insulation. They are the building blocks of cell membranes. The lipid family includes fats, oils and waxes. Steroids are also lipids. One important feature of lipids is that they can either attract or repel water. This makes them excellent for cell walls. Lipid molecules in cell walls line up spontaneously so that one side keeps water out. This lipid barrier also will not allow other molecules to pass through it, and this keeps cells intact.


    • Proteins include fish, meat, eggs and nuts.
      Proteins include fish, meat, eggs and nuts.

      Proteins keep your metabolism steady. They also are used in the building of all of your body parts. Proteins include fish, beef, eggs and nuts. Amino acids make up proteins by bonding together in spirals and other shapes. Some proteins contain as many as 5,000 amino acids in one molecule. When people or animals eat proteins, their bodies break the proteins down into amino acids, which are then carried to the cells. The cells use these amino acids to repair old or damaged cells. This makes protein molecules one of the most important organic molecules for healthy bodies.

    Nucleic Acids

    • Nucleic acids form DNA and RNA molecules.
      Nucleic acids form DNA and RNA molecules.

      When you talk about genetics, you are talking about nucleic acids, which include DNA and RNA. The nucleic acid DNA carries all the genetic information that forms living things (except for viruses). All the information that makes you who you are gets stored in these nucleic acids. RNA acts like a genetic messenger, moving around in cells, carrying the information contained in the DNA to other cell locations.

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