Week 5 · Biology Lab & Inquiry

Week 5 Biology Lab & Inquiry: Catalase & the Temperature of Life

Introduction to Biology Free sample edition

Part 1 — The Big Picture

This week you learned that an enzyme is a protein that lowers the activation-energy hill, and that its rate rises to an optimum and then crashes when heat destroys its shape, while cold only slows it. In this lab you test that idea in your own kitchen. Catalase in a raw potato splits hydrogen peroxide into water and oxygen, and the oxygen makes foam you can measure with a ruler. You write a hypothesis, measure the foam from potato held at four temperatures, summarize each condition with an average and a range, sketch the curve, and decide what your evidence supports. Then you check a chatbot's account of your experiment and catch where it mislabels the enzyme, scrambles its steps, blurs slowed with denatured, or invents a number.

Time budget: Plan for about 120 minutes.

Part 2 — The Task

Guiding question: How does the temperature of a potato change how fast its catalase splits hydrogen peroxide, and which of your results show an enzyme that was slowed and which show one that was destroyed?

Before you begin — hypothesis: Before any peroxide touches a potato cube, write your hypothesis in the if… then… because… form: if the potato is cold, at room temperature, near body temperature, or boiled, then the foam will be higher, lower, or absent, because of a reason about the enzyme you can state. Then write the prediction your hypothesis makes for the four averages.

Workshop data: Your own potato foam heights, or the illustrative fallback heights

Source: Twelve foam heights you measure yourself at a kitchen counter with the procedure in Part 3; if you cannot run the protocol, use the twelve illustrative fallback heights printed in the fallback, which were constructed for this lab and are not real data.

Rows: 12 trials, 3 at each of 4 temperatures, shown as 4 rows of the data table (one row per condition); the first scaffold table has 7 rows that name the parts of the experiment rather than data
Columns: condition, three trial heights in centimeters, sum, average, and range
Unit: centimeters of foam above the liquid, measured 60 seconds after the potato cube goes in

Part 3 — Materials & Procedure

Tools and materials

Free virtual labs and simulations (PhET, HHMI BioInteractive, Learn.Genetics), a virtual microscope, and a spreadsheet (Google Sheets or any free spreadsheet)
A raw potato, a knife and cutting board, four clear cups, household hydrogen peroxide, a ruler, a timer, ice water, warm tap water, a pot of boiling water, and paper towels
A document or notebook for your written answers

Ways of working

virtual-simulation-inquiry
at-home-protocol-and-data-table
figure-and-diagram-interpretation

Procedure

Cut four same-size cubes of raw potato, each about the size of a sugar cube, and label four cups cold, room, body, and boiled. Put the cold cube in ice water, leave the room cube on a paper towel on the counter, put the body cube in warm tap water that feels like a warm bath, and boil the fourth cube for five minutes, then let it cool back to room temperature. Take care with boiling water, and keep hydrogen peroxide away from your eyes and mouth. Tool: Free virtual labs and simulations (PhET, HHMI BioInteractive, Learn.Genetics), a virtual microscope, and a spreadsheet (Google Sheets or any free spreadsheet). Check: Four labeled cups and four equal potato cubes, each held at its own temperature for about ten minutes.
Before any peroxide goes in a cup, write your hypothesis and prediction in the first table in Part 4, and fill in the independent variable, the dependent variable, at least three controlled variables, the baseline, and one confound you will keep out. Tool: Free virtual labs and simulations (PhET, HHMI BioInteractive, Learn.Genetics), a virtual microscope, and a spreadsheet (Google Sheets or any free spreadsheet). Check: The first table has an if… then… because… hypothesis and every part of the experiment named.
Pour the same amount of hydrogen peroxide into each of the four cups, about a finger's depth. Pat the cold cube dry, drop it into the cold cup, start the timer, and after 60 seconds hold the ruler against the cup and record the height of the foam above the liquid in centimeters. Tool: Free virtual labs and simulations (PhET, HHMI BioInteractive, Learn.Genetics), a virtual microscope, and a spreadsheet (Google Sheets or any free spreadsheet). Check: One foam height in the data table for the cold condition.
Repeat step 3 for the room, body, and boiled cubes, each in its own cup of fresh peroxide, measuring at 60 seconds each time. Then cut fresh cubes and run the whole set two more times, so every condition has three trials. Tool: Free virtual labs and simulations (PhET, HHMI BioInteractive, Learn.Genetics), a virtual microscope, and a spreadsheet (Google Sheets or any free spreadsheet). Check: Twelve foam heights in the data table, three per condition.
Open a blank sheet. Type the cold trials into cells B2, C2, and D2, then room, body, and boiled into rows 3, 4, and 5. In E2 type =SUM(B2:D2), in F2 type =AVERAGE(B2:D2), and in G2 type =MAX(B2:D2)-MIN(B2:D2), then copy E2 through G2 down to row 5. Select the condition names and the averages and choose Insert, then Chart, to sketch the curve. Tool: Free virtual labs and simulations (PhET, HHMI BioInteractive, Learn.Genetics), a virtual microscope, and a spreadsheet (Google Sheets or any free spreadsheet). Check: Each average equals its row's sum divided by 3, matching your hand calculation, and the chart shows one bar per condition.
Complete the comparison table, answer the analysis questions in your document, then paste your completed tables into an approved chatbot with the prompt in Part 6 and check its answer against the scripted checks. Tool: Free virtual labs and simulations (PhET, HHMI BioInteractive, Learn.Genetics), a virtual microscope, and a spreadsheet (Google Sheets or any free spreadsheet). Check: Three completed tables, written answers, and a list of the chatbot's errors with corrections.

Fallback route

When to use it: Use this route if you cannot get a raw potato, household hydrogen peroxide, or a way to boil water, or if you cannot run the trials at home.

Use the twelve illustrative fallback heights below, constructed for this lab and not real data, as your data table, then complete every scaffold table, analysis question, and the critique step from them and submit the same items for equal credit.

This route earns the same credit as the primary route.

Twelve illustrative fallback foam heights, constructed for this lab, that stand in for your own trials.

Fallback model data
Condition	Trial 1 (cm)	Trial 2 (cm)	Trial 3 (cm)
Cold, about 5 °C	2	3	4
Room, about 22 °C	5	6	7
Body, about 37 °C	11	12	13
Boiled, then cooled	0	0	0

Part 4 — The Scaffold

Name every part of the experiment before you measure anything, so the test is fair from the first cube.

Student scaffold table 1
Part of the experiment	Your answer
Hypothesis (if… then… because…)
Prediction for the four averages
Independent variable
Dependent variable
Controlled variables (at least three)
Baseline condition the others are compared with
One possible confound you will keep out

Record each trial as you go, then add the trials, divide by 3, and subtract the smallest from the largest.

Student scaffold table 2
Condition	Trial 1 (cm)	Trial 2 (cm)	Trial 3 (cm)	Sum of the three trials	Average (sum ÷ 3)	Range (largest − smallest)
Cold, about 5 °C
Room, about 22 °C
Body, about 37 °C
Boiled, then cooled

Compare the conditions and decide which results show a slowed enzyme and which show a destroyed one, writing each step so a reader can check it.

Student scaffold table 3
Comparison	Your arithmetic	Result in words
Body average ÷ cold average
Body average ÷ room average
Cold result: slowed or denatured, and why
Boiled result: slowed or denatured, and why
Shape of the four averages in order of temperature

Part 5 — Analysis Questions

Using your data table, compute how many times the cold foam the body-temperature foam is, and how many times the room foam. Show every addition and division.
Picture your averages as a bar chart: four bars in order of temperature, cold, room, body, and boiled. Describe in words how tall each bar is, which bar is tallest, and what happens to the height between the body bar and the boiled bar.
Explain the difference between your cold result and your boiled result using the words slowed and denatured, and predict what would happen if you warmed the cold cube and the boiled cube to body temperature and tested them again. Then write one conclusion sentence that uses supports or fails to support rather than proves.
Connect your curve to the human body: why might a fever a few degrees above the body's usual 37 °C leave you feeling weak, and how does this lab show that an enzyme's shape is its job?
Choose one and answer it in 3–4 sentences. (a) Name one confound that could have crept into your own setup, such as cubes of different sizes or peroxide poured to different depths, and say how you would keep it out next time. (b) Explain why the lab uses three trials per condition, and say whether running more trials would change what you can claim.

Part 6 — AI-Critique Moment

Choose one equal-credit critique route. Route A: ask an approved AI tool to critique your completed work, then check its response against your own evidence. Route B is the no-AI equivalent printed below.

Approved tools: Claude, Gemini, ChatGPT, Grok, Microsoft Copilot.

Prompt to paste:

I've pasted my completed Week 5 Biology Lab & Inquiry tables above. I dropped equal cubes of raw potato into household hydrogen peroxide at four temperatures, cold, room, body, and boiled then cooled, three trials each, and measured the foam height after 60 seconds. Please do seven things. First, compute the sum, average, and range for each condition from my tables, showing the arithmetic. Second, name the enzyme, its substrate, and where on the enzyme the substrate binds. Third, list in order what happens to one catalase molecule from the moment it meets one hydrogen peroxide molecule until it is ready for the next. Fourth, explain why the cold and boiled cubes made so little foam, and say whether the two results have the same cause. Fifth, give the exact optimum temperature of potato catalase, with its source. Sixth, say whether my results prove that catalase works best at body temperature. Seventh, as a stretch question for later in the course, say how many cells a body cell makes when it divides for growth, and what phenotype ratio a cross of two Tt parents gives.

Test the response for these likely failures:

Chatbots often scramble the enzyme's cycle, saying the products form before the substrate binds, or ending with the enzyme used up instead of released for reuse.
Chatbots often swap the labels, calling hydrogen peroxide the enzyme or catalase the substrate, or saying the substrate binds anywhere on the enzyme rather than at one site.
Chatbots often say the cold and boiled cubes failed for the same reason, that cold also denatures the enzyme, or that hotter is always faster.
Asked for an exact optimum, chatbots often invent a precise temperature for potato catalase or cite a study that was never given, or quietly change one of my trial heights while averaging.
Asked the stretch question, chatbots sometimes say a dividing body cell makes four cells or makes cells that differ from each other.
Asked the stretch question, chatbots sometimes give the phenotype ratio of a Tt by Tt cross as 1:2:1.

Write 3–5 sentences naming one thing the chatbot got right and at least two places it went wrong or overreached, quoting its words and correcting each with evidence from your own tables or this week's chapter; mark the stretch answers as ones to check later.

Equivalent route (no AI required)

No AI account is required for this lab. Instead of the chatbot, critique this flawed analysis, printed here in full: "In my catalase lab, the body-temperature potato averaged 12 cm of foam and the boiled potato averaged 0 cm, so my results prove that heat always speeds up enzymes and the boiled cup was a bad trial. The cold potato barely foamed because the cold denatured its enzyme, the same thing boiling does. Hydrogen peroxide is the enzyme here, and catalase is the substrate it breaks down. First the oxygen forms, then the peroxide binds to the potato, and at the end the catalase is used up. Potato catalase works best at exactly 45 °C, as a study showed. As a preview of later weeks, a body cell dividing for growth makes four identical cells, and a cross of two Tt parents gives a 1:2:1 phenotype ratio." Mark it up: quote each flawed sentence, name what is wrong (an oversimplified mechanism or a proof claim, a mislabeled enzyme or substrate, the enzyme's steps out of order, an invented figure, or a preview fact stated wrong), cite the evidence from your tables or this week's chapter, and write a corrected sentence beneath it; for the two preview sentences, say which later week will check them. This route assesses the same objectives (Objective 4 and Objective 1) as the chatbot critique, takes comparable effort (about 30 minutes and 200–300 words), is scored by the same scoring criteria for the same credit, and its own submission artifact is the marked-up flawed analysis, posted in place of the chatbot share link and report.

Part 7 — What to Submit

All three completed scaffold tables, filled from your own trials or the illustrative fallback heights
Written answers to all five analysis questions
The chatbot critique report with its share link, or the equivalent route's marked-up flawed analysis

Deliverable:

A short Biology Lab & Inquiry report on the catalase temperature test: three completed tables (the named parts of the experiment, the twelve foam heights with sums, averages, and ranges, and the comparison of the conditions), written answers to five analysis questions, and a critique of a chatbot's account of your experiment, or, on the equivalent route, a marked-up correction of the printed flawed analysis. 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. Choose a written, recorded, or visual form for your answers; every form is graded by the same scoring criteria.

Rubric

The rubric below shows how each submitted part is evaluated; bands are full, partial, or none.

Workshop evaluation criteria
Criterion	Full	Partial	None
Testable hypothesis and the parts of the experiment	A falsifiable if… then… because… hypothesis and a prediction for the four averages appear before the data, and the independent variable, dependent variable, at least three controlled variables, the baseline, and a confound are each named correctly.	A hypothesis appears but is not falsifiable or lacks a prediction, or one or two parts of the experiment are missing or swapped.	No hypothesis, or the parts of the experiment are not named.
Completed data table with correct arithmetic	All twelve heights are recorded from the student's own trials or the fallback heights, and every sum, average, and range is correct with the steps visible.	The table is filled, but one or two sums, averages, or ranges are wrong or their steps are missing.	No data are recorded, or the numbers are invented rather than measured or taken from the fallback.
Analysis in words	Questions 1 to 4 are answered accurately: both comparisons with steps, a word description of the four bars that names the peak and the crash, cold explained as slowed and boiled as denatured with a supports-style conclusion, and the fever connection tied to enzyme shape.	The questions are attempted, but one or two answers blur slowed and denatured, claim the data prove the hypothesis, or say hotter is always faster.	The analysis questions are missing or do not address the data.
Critique of the chatbot or of the printed flawed analysis	On either route, at least two errors are quoted and corrected with evidence from the student's own tables or the chapter, stretch answers are marked to check later, and one correct point is acknowledged; both routes earn this band equally.	On either route, errors are named but corrected without evidence, or only one error is caught.	No critique appears, or pasted output is submitted without any checking.
Reflection on the design of the test	The chosen reflection option is answered in 3–4 sentences that tie a specific confound or the number of trials to a concrete change in the test or in what can be claimed.	The reflection is answered but stays general or names no specific change.	No reflection is submitted.

Quality Gate

Every height in the data table comes from your own trials or the printed fallback heights, never from memory or a chatbot.
Each average equals its row's sum divided by 3, and each range equals the largest trial minus the smallest.
The hypothesis was written before the first cube went into peroxide and has the if… then… because… form.
The independent variable, dependent variable, controlled variables, and baseline are each named, with temperature as the independent variable.
The cold result is described as slowed and the boiled result as denatured, each with a reason.
No measurement, optimum temperature, study, or source is invented anywhere in the submission.
The critique quotes the chatbot or the flawed analysis and corrects at least two errors with evidence from your tables or the chapter.

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