Instructor Notes — Chapter 1

Teaching notes

What this chapter is actually for

It looks like a biochemistry review. It is not. It is a demonstration that chemical reasoning eliminates claims before evidence is consulted, and the whole chapter is built to make students experience that once, concretely, so the rest of the book has somewhere to stand.

If students leave able to recite the twenty amino acid families but unable to explain why an oral peptide claim is suspect, the chapter has failed. Prioritize §1.1, §1.3, and §1.6 over §1.2's taxonomy. Nobody in this course needs to memorize side chains.

Common misconceptions

"Peptides and proteins are fundamentally different kinds of molecule." They are not. Students arrive expecting a real chemical boundary and are often unsettled to learn it is a convention. Lean into that discomfort — it is the first instance of a pattern the whole book relies on, which is that useful categories are frequently conventional and that people exploit the ambiguity.

"Natural means safe." Nearly universal on arrival, and rarely dislodged by simply asserting the opposite. The effective move is the list: botulinum toxin, ricin, cone snail venom, digitalis. Then the harder point — that most peptide drugs are deliberately unnatural, engineered specifically so the body cannot handle them the usual way.

"If it works in a dish, it works in a person." This surfaces early via the collagen case and is the chapter's most important seed for Chapter 5. Plant it here.

"Sequence and composition are the same thing." They are not, and exercise 1.13 catches it. Worth five minutes because it makes Sanger's achievement legible and prefigures why amino acid analysis is a weaker identity test than sequencing (Ch 34).

The reverse error, which is subtler and more common in strong students: that chemistry settles questions. Case Study 2 exists specifically to break this. Students who arrive skeptical will want the collagen case to be a clean debunk; it isn't, and their frustration with that is the lesson.

The hardest point to teach

That a ❌ is a statement about evidence rather than about a molecule.

Students hear "no human trials" and translate it instantly to "doesn't work." The translation is wrong and it is nearly automatic. Chapter 1 only introduces the distinction (§1.9), but the groundwork has to be laid here because Chapter 17 depends entirely on it.

The framing that works best: ask students what the evidence was for insulin in 1920. Answer: none, in humans. It worked anyway; the trials simply hadn't happened yet. Absence of evidence described the literature, not the molecule. Then ask what distinguishes 1920 insulin from a 2026 compound with no human trials — and let them work out that the honest answer is nothing about the molecule; only what happened next. That discomfort is correct and should not be resolved.

A demonstration that works

The paper-chain build. Give small groups twenty index cards labeled with amino acid three-letter codes, color-coded by family (nonpolar, polar, acidic, basic). Have them physically build a chain, then:

1. Ask them to reverse it and state whether it is the same molecule. (No — direction matters.)
2. Ask them to swap two cards and predict what happens. (Unknowable without knowing what those residues do — which is the honest answer and the point.)
3. Hand them scissors, tell them the scissors are pepsin, and ask what happens if the chain is swallowed.

Step 3 lands harder than any diagram. Ten minutes, no materials cost, and students remember it.

A second, faster one: put the size spectrum on the board and have students place five molecules on it from memory — aspirin, insulin, semaglutide, growth hormone, an antibody. Then ask which can be a tablet. The answer falls out of the placement, which is exactly the reasoning move the chapter teaches.

Timing

For a 75-minute session:

Do not skip the dossier launch. If students choose their peptides in class rather than as homework, participation across the whole term is markedly better, because the entries are personal from day one.

Assessment notes

Exercises 1.11, 1.20, 1.22, and 1.32 are the ones that reveal whether the method landed. 1.32 in particular separates students who understood the argument from students who memorized the slogan — it asks them to argue against the book's own framing, and a student who can only agree has not got it.

Exercise 1.36 (noticing your own bias in confidence scores) should be graded on honesty and not on conclusion. Say so explicitly, or you will receive thirty identical paragraphs claiming no bias.