How Should Biochemical Topics Be Treated in an Organic Textbook?

In most organic chemistry courses, the majority of students are biology majors and/or have their sights set on a career in medicine or other health-related field. My own course is no different. Therefore, like many organic instructors, I believe that students ought to see the relevance of organic chemistry to biology and medicine. Why is the course required for a degree in biology? Why is the course a prerequisite for medical school? One way for students to see this relevance is to show them how organic chemistry specifically applies to biology and medicine. One way to do this is by exposing students to some biochemical topics. But how? To what extent? And when?

In a traditional organic text, the majority of biochemical topics are relegated to the final few chapters of the book. These books typically allot one chapter for each class of biomolecules—proteins, carbohydrates, lipids, and nucleic acids. I see three major problems with this organization. One is that for students whose interests are in biology or medically related fields, the relevance isn’t realized or appreciated until the final few weeks of the second semester! I think that’s much too long for students to wait. The second major problem I see with this organization is that there is often not enough time in the semester to cover these biochemical topics. Many instructors have told me that they have to rush just to get through the “standard” organic chemistry topics and, at best, they have maybe a lecture or two to cover any of the topics from the biomolecules chapters. Some instructors simply run out of time, never getting to that material at all. The third problem I have is that there is too much material in those biomolecules chapters, a large percentage of which constitutes significant portions of a biochemistry-specific textbook, so many instructors feel that a lot of the material simply doesn’t belong in an organic textbook.

Some textbooks attempt to remedy the relevance issue in different ways. One way is to fully integrate the biochemical discussions throughout the main narrative of the text in each chapter, using biomolecules and biochemical processes as contexts in which to introduce organic topics. I’m not a big fan of this as a solution because I think it has the potential of becoming a barrier to students’ learning. The organic chemistry topics themselves can be challenging enough, even in the context of small and simple molecules. The larger and more complex biomolecules can take the material from being challenging to being daunting.

Another solution I have seen is to keep the biomolecules chapters at the end of the book, but scatter small “sound bites” of biochemistry in short asides throughout the entire book. This has the potential for addressing the relevance issue, but in practice, I think it falls short for two reasons. First, unless students are actually assigned those asides (and are held accountable), most will not, realizing that the material will not be on the exam. Second, because those asides often give cursory presentations of relatively complex biochemical phenomena, it is difficult for students to come away with a true appreciation of the topic.

In my textbook, I tackle the problem in an entirely different way by placing biochemically-related topics in the main part of the text, but in self-contained sections at the ends of select chapters, beginning with Chapter 1. The topics are chosen to satisfy two criteria: (1) They relate directly to the organic chemistry material discussed in the chapter, which will have been introduced in the context of smaller and simpler organic molecules, and (2) they are topics that the ACS exam and the MCAT tend to expect students to have learned. In fact, these topics align almost perfectly with the organic chemistry expectations outlined in the guide for the new MCAT exam, “MCAT²⁰¹⁵.” Examples of such topics are: Classifying terpenes, the relationships of anomers and epimers, the forms of amino acids at various pH, glycoside formation and hydrolysis, and peptide synthesis and analysis.

Treating the biochemically related material in this way has several advantages. One advantage is that it affords an instructor the opportunity to teach these topics much earlier in the year—as early as the first week or two of class in the first semester. Students would therefore be able to more immediately see the relevance of the organic chemistry. Additionally, instructors can feel more comfortable asking their students to spend time on these sections, given the relevance of the topics to the ACS and MCAT²⁰¹⁵ exams. A second advantage is that the topics can provide instructors a means by which to reinforce the organic chemistry from earlier in the chapter. With tighter focus on the organic chemistry of biomolecules, a third advantage is a dramatic decrease in the amount of biochemical content in the book. And yet another advantage is that the main narrative of the chapter does not depend on the coverage of the bioorganic chemistry section, so a section can be covered or skipped at the instructor’s discretion.

— Joel Karty