Biology: monomers and polymers

Tutoring Biology 12, you cover this concept.  The tutor approaches it from a simple, practical point of view.

You normally hear about monomers and polymers in organic chemistry.  Think of the name polyester:  it’s a polymer of esters.  The esters, then, are the monomers.

A commonly used analogy is a necklace of beads.  The entire necklace, altogether, is the polymer.  The beads are the monomers.  They don’t have to be the same as each other, but are similar.

So, a polymer is a molecule consisting of many monomers bonded together. The monomers found in a polymer are of the same chemical family, if they’re not the same.

Let’s accept the idea that the biological molecules fall into four basic categories: carbohydrates, lipids (aka fats and oils), proteins, and nucleic acids.  Three of these can easily be imagined as polymers, with their monomers shown below:

Polymer Monomer
carbohydrate (incl. starch, sugar, or glycogen) simple sugar, aka, monosaccharide; eg, glucose
nucleic acid (DNA, RNA) nucleotide
protein amino acid

So, you might say that “protein is to amino acid as carbohydrate is to monosaccharide.” Or, “DNA is to nucleotide as necklace is to bead.” However you imagine it, familiarity with the concept – as well as the specific cases – is important for biology and organic chemistry students.

While lipids are made from smaller units, the units are not all from the same chemical family. Hence, lipids don’t easily fit the “polymer” idea the way that carbohydrates, proteins, or nucleic acids do. However, I’ll talk more about lipids in a future post.

Good luck to all my students in this weekend’s biology conference:)

Source:

Mader, Sylvia S. Inquiry into Life, 11th Ed. New York: McGraw-Hill, 2006.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

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