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Biochemical Compound Classification

There are four major categories of biologically important molecules.

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Bonded for Life

Bonded for Life


Credit: Spiffistan
Source: http://commons.wikimedia.org/wiki/File:Bdna_cropped.gif
License: CC BY-NC 3.0

This model represents part of a DNA molecule. Your life-and the lives of all other organisms–depend on molecular compounds such as DNA.

Why It Matters

  • The majority of your body consists of water. The other compounds that make up you and other living things are called biochemical compounds. They are placed in four classes: proteins, carbohydrates, lipids, and nucleic acids. DNA is classified as a nucleic acid.
  • All of these compounds in living things are molecular compounds. Molecular compounds form between nonmetallic elements that are held together by covalent bonds.
  • Credit: Ryan Somma
    Source: http://www.flickr.com/photos/ideonexus/7343716078/
    License: CC BY-NC 3.0

    3D model showing the covalent bonds in a water molecule [Figure2]

  • The nonmetal carbon is the basis of all biochemical compounds. Carbon can form covalent bonds with itself and many other atoms, creating an incredible array of biochemical molecules.
  • Review covalent bonds by watching this video: 


Can You Apply It?

Learn more about covalent bonds and biochemical compounds at the links below. Then answer the questions that follow.

  1. What is covalent bonding?
  2. What’s the difference between polar and nonpolar covalent bonds?
  3. Define electronegativity. How is electronegativity related to the polarity of a covalent bond?
  4. The nature of covalent bonds influences the properties of covalent, or molecular, compounds. What are general properties of molecular compounds?
  5. Biochemical molecules often consist of many smaller molecular compounds, called monomers. The monomers are joined together in long chains by covalent bonds. What are the monomers of proteins? Of nucleic acids?
  6. Identify the general function of each of the four main classes of biochemical compounds.

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Image Attributions

  1. [1]^ Credit: Spiffistan; Source: http://commons.wikimedia.org/wiki/File:Bdna_cropped.gif; License: CC BY-NC 3.0
  2. [2]^ Credit: Ryan Somma; Source: http://www.flickr.com/photos/ideonexus/7343716078/; License: CC BY-NC 3.0

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