Week 4 — Spend It, Make It, Read It: An ATP and Gene-Decoding Report — Traditional alternative (no AI)

Instructors: publish this instead of the adaptive version if you prefer, and unpublish or delete the adaptive one.

Assignment 4 of the term — pay for work with ATP, do the glycolysis bookkeeping, decode a gene, and put a sprint's burn into plain words for someone new to anatomy and physiology.

This week you learned why ATP is spendable currency, how cellular respiration runs in three ordered, located stages, what a sprint does when oxygen is short, and how a gene is transcribed and translated into a protein. Week 2 gave you ATP and proteins as molecules, and Week 3 gave you the organelles and the pump that spends ATP; this week you see the steps inside those jobs. In this assignment you work four short problems, interpret each one, and explain a sprint's burn to someone who has never studied anatomy and physiology. This week's lecture tutorial, quiz, discussion, and A&P Lab & Inquiry practise the same ideas from other angles.

The task

This week's shared dataset is Dataset D, the gene decoded. The DNA template strand, read 3′ to 5′, is TAC CGA GTA TTC CCA ATT; its mRNA, read 5′ to 3′, is AUG GCU CAU AAG GGU UAA; and the standard codon table reads it as Met–Ala–His–Lys–Gly, then stop. Glycolysis, in the cytoplasm, makes 4 ATP and uses 2 for each glucose, and the sodium-potassium pump moves 3 sodium ions out and 2 potassium ions in per ATP. The glucose counts in the problems are illustrative.

Work these four problems, showing your arithmetic:

1. The sodium-potassium pump moves 3 sodium ions out and 2 potassium ions in for each ATP it spends. If it spends 2 ATP, how many ions does it move in all, out and in together?
2. Glycolysis makes 4 ATP and uses 2 ATP for each glucose. For an illustrative cell that runs glycolysis on 3 glucose, what is its net gain of ATP?
3. The pinned mRNA has 6 codons, and each codon is 3 bases long. How many bases does the mRNA carry?
4. The pinned mRNA has 6 codons, and its last codon, UAA, is a stop codon that adds no amino acid. How many amino acids does translation build from it?

Beside each answer, add one brief interpretation:

• Problem 1: say what each ATP becomes as it releases energy, and explain why ATP works as spendable currency rather than a battery stored for days.
• Problem 2: say where glycolysis happens and whether it needs oxygen, and explain why 4 is the gross figure and not the net.
• Problem 3: say where transcription happens, and explain why the mRNA carries U where the template carries A and never carries a T.
• Problem 4: say where translation happens and name the chain the codon table gives, and explain why the stop codon adds no amino acid.

Explain it to a non-expert

A teammate asks, "Why do my legs burn when I sprint one lap, but not when I jog four easy laps?" Write a 3–5 sentence message that explains what ATP is in everyday words, what happens to pyruvate when oxygen is short, and why the oxygen-using route makes far more ATP. Name one limit, for example that the total ATP per glucose is an estimate taught in words, or that this message is about how cells work and not about anyone's health. Put any technical term in everyday words. More than one good message is possible.

For a different, ungraded example, imagine a friend who asks why a cell copies a gene instead of using the DNA directly. Model answer: "Think of the DNA as a cookbook that never leaves a locked library, the nucleus. When the cell needs one protein, it copies that one recipe onto a card, called messenger RNA, and carries the card out to the kitchen, the ribosome, where the protein is built. The book stays safe, and the card can be read wherever the work happens. This is a classroom picture, a simplification, and it does not explain how a cell decides which recipe to copy."

Use that pattern for the sprint message, with your own wording and evidence.

Show your arithmetic. A reader should be able to rebuild every number you report from the values given, without guessing which values you used or which operation you chose.

Deliverables

Submit a single report containing:

• the four answers, each with the arithmetic shown and the brief interpretation the task names for that problem;
• your message to your teammate, explaining what ATP is, what happens to pyruvate when oxygen is short, why the oxygen-using route makes far more ATP, and one limit; and
• a one-line restatement of the values you used, so your results are reproducible.

Keep it to roughly one page.

Choose how you show it. Present your report as written text, or as a recorded audio or video explanation of about three minutes with a transcript, or as a labeled sketch of the codon-by-codon decode with a short note. Every form is graded by the same scoring criteria. 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.

How you'll be graded

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

Academic integrity and AI use

This version is designed to be completed without AI: do the computations, the interpretations, and the writing yourself, without a chatbot or other AI tool. You may use a calculator or a spreadsheet for the arithmetic. Submitting AI-generated work as your own, or copying another student's work, is an integrity violation under the course policy.

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