Amino Acids Are Like the Letters of the Alphabet

Written by SuEarl McReynolds, Palo Alto College, San Antonio, TX

When I’m talking about proteins, I tell the students that there are only 20 different amino acids. Yet from just those 20 “building blocks”, an infinite number of proteins can be formed. At first that idea is hard to grasp. Then I ask how many letters there are in the alphabet. They reply “26”. Then I ask how many words can be formed from those 26 letters. The light goes on. Then I comment on the fact that there are 26 letters but only 20 amino acids, but in forming words what makes the difference is the particular letters that are used, the number of those letters and the sequencing of those letters. All of the same variables are true in forming proteins from amino acids—PLUS the three-dimensional arrangement of the amino acids. It’s like playing 3-dimensional Scrabble.