Carbohydrates, Proteins, and Nucleic Acids are all made from building blocks.  Building blocks can be called monomers.  Regardless of the monomer, you should be able to picture how they can add together into a long chain to make a large molecule.  A long chain of monomers is called a polymer.  And a polymer is what comprises a macromolecule.  Let's see how this works.

    Let's say that one monomer is represented by this rectangle:  .   We could even have different versions of this monomer, like this or this .  This is kind of like boxcars of a train.  A boxcar is the building block for a train, and even though there can be variations on a boxcar (for freight, passengers, etc.), it is still a boxcar and can still be put together with other boxcars to make a train.  We could put our monomers together to make a macromolecule.  Here are three different ways we could string some monomers together into macromolecules:

The stringing together is simply chemical bonding between the monomers.   Once there is a long chain of monomers, that is either a carbohydrate, protein, or nucleic acid-- depending on which monomer it is built from.  Keep in mind that the long chain can be bent, folded, branched, or twisted, but it is still simply a long joining of building blocks.

    Therefore, if you know which monomer is used to make each of the remaining macromolecules (carbohydrates, proteins, nucleic acids), you have gone a long way toward understanding the structure of that macromolecule.  Each of the macromolecules uses a different monomer.

Note that lipids are not in this chart, because lipids are not built from monomers.  Also, note that your book does not use the term "monomer."  But it is important enough that I want you to learn it.  They certainly talk about building blocks in the book, and a building block is a monomer.

    Finally, to be sure that you followed the train analogy above as it applies to macromolecules, if we said that the rectangle represented an amino acid, then each of the different colors of rectangles represents a slightly different amino acid-- but they would all be amino acids.  And a long chain of amino acids is a polymer for building a protein. 

© 2006 STCC Foundation Press, content by Dawn A. Tamarkin, Ph.D.

Last changed: January 21, 2007