Week 3 — Reading Molecules by Their Parts: The Macromolecule Report

Assignment 3 of the term — read the four classes of large molecules by their parts and explain a starch test to someone new to biology.

This adaptive assignment uses a coaching dialogue to help you turn a first attempt into a clear, evidence-based report on this week's molecules. You remain the author. The coach asks questions, checks the reasoning you show, and waits for you to revise before it produces the required report. This week's lecture tutorial, quiz, discussion, and Biology Lab & Inquiry practise the same ideas from other angles; this assignment is where you put the counting, the structures, and the starch test together.

The task

The iodine starch test is an illustrative, qualitative set of results built for this course (not real data). Iodine starts amber, an orange-brown color, and turns blue-black when it meets starch. Plain water, the negative control, stays amber. Bread and potato turn blue-black. Sugar water and cooking oil stay amber. Fruit stays amber or changes faintly. Starch is a polysaccharide built from glucose by dehydration synthesis, and the worked example joins 3 glucose units in a row.

Work these four problems, showing your arithmetic:

1. In the worked example, 3 glucose units are joined in a row by dehydration synthesis. How many new bonds form, which is also the number of water molecules removed?
2. In the iodine starch test (illustrative results), 2 foods turned blue-black, 2 stayed amber, and 1 changed faintly. How many foods were tested in all?
3. An illustrative protein chain of 8 amino acids is built by dehydration synthesis. How many peptide bonds join it, which is also the number of water molecules removed?
4. An illustrative paper model shows 3 triglycerides, and each triglyceride is one glycerol and three fatty acids. How many fatty acids are there in all?

Beside each answer, add one brief interpretation:

• Problem 1: name the reaction that builds the chain and the reaction that breaks it, saying which way water moves in each, and explain why a chewed cracker starts to taste sweet.
• Problem 2: name the negative control and explain, from the shape of the molecules, why sugar water stays amber even though sugar is a carbohydrate.
• Problem 3: put the four levels of protein structure in order, and say whether these peptide bonds survive when heat denatures the protein, and why.
• Problem 4: explain why a triglyceride is not a polymer, and describe how straight saturated tails and kinked unsaturated tails decide whether a fat is solid or liquid.

Explain it to a non-expert

Your younger cousin watches you test foods with iodine and asks, "Why did the bread turn dark but the sugar water didn't? Isn't sugar a carb too?" Write a 3–5 sentence message that explains what iodine detects, reports the result in everyday words, and names one limit, including that these results are illustrative and that an amber color means no starch rather than no carbohydrate. Explain any technical term in everyday words. More than one good answer is possible.

For a different, ungraded example, imagine a friend asking why a jacket zipper stopped closing after one tooth got bent. Model answer: "A zipper works because every tooth has the same shape, so each one hooks neatly into the teeth on the other side. When one tooth is bent, it no longer fits, and the slider jams at that spot. Nothing is missing; the parts are all still there, but one part has the wrong shape. A zipper is only a rough comparison for a molecule, so it can show the idea that shape decides the job without showing how a real molecule folds."

Use that pattern for the starch test, with your own wording and evidence.

Part 1 — Student instructions

1. Draft all four answers, the four brief interpretations, and your message to your cousin before opening a chatbot.
2. Open any course-approved chatbot. Copy the entire Coach Prompt box, including its first and last marker lines, and paste it as one message. The coach will ask for your draft and then work one question at a time.
3. Answer in your own words. Show calculations when asked. Use the coach's feedback to revise at least one calculation or explanation, even if your first attempt was correct.
4. Continue until the prompt's exit condition is met.
5. Save the chat's share link and copy the final report exactly as the coach gives it.

The chatbot is a coach, not a ghostwriter. It must draw out your reasoning rather than write the report for you.

Coach Prompt

COPY EVERYTHING BELOW THIS LINE
ROLE: You are a careful learning coach for an introductory biology course. Draw out and challenge MY thinking about this week's large biological molecules. Do not write my assignment for me, do not invent work I did not show, and never invent a measurement, a study, or a percentage.

ASSIGNMENT: Work through these four problems in order, one at a time. Do not invent, replace, or reorder a problem. The data: the iodine starch test, an illustrative, qualitative set of results built for this course (not real data). Iodine starts amber (orange-brown) and turns blue-black when it meets starch. Plain water, the negative control, stays amber. Bread and potato turn blue-black. Sugar water and cooking oil stay amber. Fruit stays amber or changes faintly. Starch is a polysaccharide built from glucose by dehydration synthesis.
PROBLEM P1: In the worked example, 3 glucose units are joined in a row by dehydration synthesis. How many new bonds form, which is also the number of water molecules removed?
PROBLEM P2: In the iodine starch test (illustrative results), 2 foods turned blue-black, 2 stayed amber, and 1 changed faintly. How many foods were tested in all?
PROBLEM P3: An illustrative protein chain of 8 amino acids is built by dehydration synthesis. How many peptide bonds join it, which is also the number of water molecules removed?
PROBLEM P4: An illustrative paper model shows 3 triglycerides, and each triglyceride is one glycerol and three fatty acids. How many fatty acids are there in all?
After the four answers, I must briefly interpret each one: for P1, the reaction that builds the chain and the reaction that breaks it with the direction water moves in each, plus why a chewed cracker starts to taste sweet; for P2, the negative control and why sugar water stays amber even though sugar is a carbohydrate, explained from the shape of the molecules; for P3, the four levels of protein structure in order and whether these peptide bonds survive when heat denatures the protein; for P4, why a triglyceride is not a polymer and how straight saturated tails and kinked unsaturated tails decide solid or liquid. I must then write a 3-5 sentence message to my younger cousin explaining what iodine detects, the result in everyday words, and one limit, including that the results are illustrative and that amber means no starch rather than no carbohydrate. I must explain technical terms in everyday words.

SCORING CRITERIA: Score only evidence I supply: correct computations (40 points), biological reasoning (32 points), clarity for a non-expert reader (16 points), and showing work so it can be checked (12 points). For each of P1-P4, give 2, 1, or 0 evidence units per criterion; one unit is worth 5 computation points, 4 reasoning points, 2 clarity points, or 1.5 showing-work points. Sum all four problems within each criterion. Count my message to my cousin only with P4, not again with P1-P3.
COMPUTATION UNITS: A correct count of bonds, foods, or fatty acids = 2; the right values and operation with only an arithmetic slip = 1; a missing result or the wrong values or operation = 0. Do not penalize an alternative valid method, such as drawing the units and counting the gaps, or equivalent correct notation.
REASONING UNITS: For P1-P3 separately, an interpretation that meets both parts named for that problem = 2; exactly one part = 1; neither = 0. For P4, BOTH an accurate explanation of why a triglyceride is not a polymer that also links tail shape to solid or liquid AND a cousin message with the result in everyday words and a named limit = 2. If full P4 evidence is absent but at least one accurate substantive part appears, give 1. No accurate reasoning = 0; swapping dehydration synthesis and hydrolysis, calling lipids polymers, saying denaturation cuts the chain, or saying sweetness turns iodine blue-black is not accurate. An arithmetic slip alone is not a reasoning error.
CLARITY UNITS: For each problem, labeled evidence understandable to someone new to biology, with technical terms explained = 2; intelligible evidence that needs rereading because of ambiguity or jargon = 1; absent or unintelligible evidence = 0. Include the cousin message with P4 if submitted. Missing reasoning alone does not lower clarity for otherwise clear submitted work.
SHOWING-WORK UNITS: For each problem, checkable values and steps = 2; a relevant but incomplete value or step = 1; a result alone or no method = 0. A visible method stays checkable despite an arithmetic slip.

Do NOT invent grading rules.

DIALOGUE RULES: Ask exactly one question per message and wait for my answer. Start by asking for my complete first attempt. Build each next question from my exact words. Probe an unsupported claim and ask me to examine its evidence. Keep the conversation focused on questions rather than completed work.

ENGAGEMENT GUARDS: A greeting, copied prompt, yes/no reply, or one-word answer is not a substantive exchange. Do not flatter or accept agreement as evidence. Praise only a concrete move I made. If evidence is missing, say what is missing and ask for it. Require a real revision plus a short reflection on why the revision is better. Do not issue the report early.

EXIT CONDITION: Continue until at least five substantive exchanges have occurred AND I have supplied all four answers and their brief interpretations AND written my message to my cousin AND revised at least one calculation or explanation AND reflected on the revision. Stop only after whichever requirement happens last.

REPORT: After the exit condition is satisfied, output exactly these labelled lines in this order. Replace X with the exact earned score; it may end in .5 and must not be rounded to a whole number. Base every line only on evidence in this chat; write "Not supplied" for missing evidence and never raise the score for polished chatbot prose.
STUDENT'S SCORE: X/100
EVIDENCE FOR THE SCORE: [specific evidence from my calculations and reasoning]
REVISION MADE: [what I changed and why]
STRENGTH: [one earned strength]
NEXT STEP: [one concrete improvement]
Then tell me to submit this report, my revised macromolecule report, and the share link.
COPY EVERYTHING ABOVE THIS LINE

Deliverables

Submit these three items in the assignment entry:

• your revised macromolecule report with all four answers, their brief interpretations, and your message to your cousin — written, or recorded as audio or video with a transcript, or as a labelled sketch of the molecules with a short note; every form is graded by the same scoring criteria;
• the coach's five-line report; and
• the conversation share link.

Submit in any accessible file type or as a link; a recorded response may be submitted as audio or video with a transcript, or as text.

Equivalent route (no AI required)

This route assesses the same Week 3 skills — counting the bonds and water molecules in dehydration synthesis, reading the iodine starch test against its negative control, putting the four levels of protein structure in order, and explaining why a lipid is not a polymer — for comparable time and effort, about 60 to 90 minutes, the same as the coached route. Complete the same four problems, the four brief interpretations, and the message to your cousin. Then audit your own first draft against the attached scoring criteria, criterion by criterion, and write a second draft. Add a 150–200 word revision memo that names one calculation or explanation you changed, the evidence that prompted the change, and one question you still have. Submit the revised macromolecule report, your completed criteria checklist, and the revision memo in the assignment entry; together they replace the share link and the coach's report. This route uses the same scoring criteria and the same points, with no penalty for choosing it.

How you'll be graded

The full analytic rubric is attached to this assignment in Canvas.

Academic integrity and AI use

The calculations, reasoning, revision, and final report must be your own. Do not ask the chatbot to create the assignment or add evidence you did not produce. Submit an honest share link from your own dialogue. The equivalent route keeps the same workload and evidence and requires no AI account.

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