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From Chemistry to Cure


Elizabeth C. Leininger
Division of Natural Sciences
New College of Florida


This case study uses the discovery and molecular structure of penicillin to teach basic chemistry concepts as they apply to biological and biologically-active molecules. Topics covered include the elements found in living things, electronegativity and polarity, the identification of chiral carbons in molecules, and the difference between structural isomers and stereoisomers. The case also helps students become more confident in interpreting skeletal diagrams (the chemical shorthand for representing molecules without explicitly drawing carbons and hydrogens) throughout their biology education. Such skeletal diagrams are often shown in introductory biology textbooks, but not "decoded" for students until later in their chemistry education. The case was developed specifically for use in a flipped classroom and there are several videos, including one created by the author, which students watch for homework so that they can better spend their time on group work in class. The case is appropriate for students in a cellular-/molecular-focused introductory biology course for majors and does not assume extensive chemistry preparation beyond what is presented in introductory biology texts.



  • Think critically about epidemiological data and gain an appreciation for the historical threat of bacterial infections.
  • Practice reading skeletal structures of molecules.
  • Recognize which elements are most commonly found in organic molecules.
  • Apply basic bonding rules (octet rule) to atoms within a molecule.
  • Distinguish between polar and nonpolar covalent bonds.
  • Identify chiral centers in a molecule.
  • Decide whether two molecular structures constitute structural isomers or stereoisomers.
  • Understand the mechanism of penicillin by relating its structure to that of the molecular targets of bacterial enzymes.



penicillin; antibiotics; chemistry; skeletal diagrams; covalent bonds; chirality; skeletal diagram; stereoisomer

Topical Areas

History of science

Educational Level

High school, Undergraduate lower division



Type / Methods

Directed, Flipped



Subject Headings

Biology (General)  |   Chemistry (General)  |  

Date Posted


Teaching Notes

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Answer Key

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The following video(s) are recommended for use in association with this case study.

  • Common Elements in Living Things
    Reviews the elements that comprise most living matter on Earth. Running time: 1:10 min. Created by Brain Genie, 2011.
  • The Chemical Bond
    Explains the concepts of covalent bonding, electronegativity, and polarity. Running time: 3:32 min. Created by Professor Dave, 2015.
  • Representing Molecule Structures
    Explains how to read and interpret structural and skeletal chemical diagrams, two ways to represent molecules in a short-hand format, and how to convert between the two diagram styles. Running time: 2:39 min. Created by Elizabeth C. Leininger for the National Center for Case Study Teaching in Science, 2017
  • Isomers
    Explains the difference between structural and stereoisomers. Running time: 6:48 min. Created by The Khan Academy, 2015.
  • Chirality
    Defines the concept of chirality. Running time: 3:10 min. Created by Lydia Flynn, 2013.