Catalase enzyme lab
01 // Question
How does the temperature of a potato disk change how fast it breaks down hydrogen peroxide?
A testable question names one thing you change (temperature) and one thing you measure (reaction speed).
02 // Variables
Independent
Temperature of the potato disk- Cold (refrigerated)
- Room temperature
- Warm (soaked in warm water)
Dependent
Time to react with hydrogen peroxide- Seconds for foam or bubbling to start
- Height of foam after 1 minute
03 // Hypothesis
IF a potato disk is warmed before being exposed to hydrogen peroxide, THEN it will produce bubbles faster than a cold disk, BECAUSE the catalase enzyme's molecules move and collide with hydrogen peroxide more often at warmer temperatures, up to the point where heat starts to damage the enzyme.
04 // Procedure
1. Cut equal disks
Cut potato disks of the same thickness and diameter using a cork borer or knife and a ruler.
2. Set the temperature
Prepare one disk cold, one at room temperature, and one warmed in a water bath.
3. Measure the peroxide
Measure an equal volume of hydrogen peroxide into a clear container for each trial.
4. Add and time
Drop in a disk and immediately start timing how long until bubbling clearly begins.
5. Measure the foam
After 60 seconds, measure the height of the foam produced in each container.
05 // Data table
| Disk temperature | Time to first bubbles (s) | Foam height at 60 s (mm) |
|---|---|---|
| Cold | ____ | ____ |
| Room temperature | ____ | ____ |
| Warm | ____ | ____ |
06 // What to expect
The room-temperature and warm disks usually react fastest, producing bubbles almost immediately, because catalase — an enzyme found in the cells of potatoes, liver, and most living tissue — speeds up the breakdown of hydrogen peroxide into water and oxygen gas.
A disk that is heated too much, such as one that has been boiled, stops reacting almost entirely, because high heat permanently changes the enzyme's shape, and an enzyme that has lost its shape can no longer do its job.
07 // Lab notes
- Safety. Hydrogen peroxide can irritate skin and eyes at higher concentrations — wear goggles and avoid contact with skin.
- Use fresh potato disks for each trial — a disk that has already reacted has used up some of its catalase.
- Do not seal the container while it's bubbling — the reaction releases oxygen gas that needs to escape.
08 // Remember
Enzymes work fast — until heat wrecks their shape. A boiled disk barely reacts at all, no matter how long you wait.
09 // Questions people ask
Why does hydrogen peroxide bubble when it touches a potato?
Potato cells contain an enzyme called catalase, which rapidly breaks down hydrogen peroxide into water and oxygen gas. The bubbles you see are the oxygen gas being released — the same enzyme protects living cells from a toxic byproduct of normal metabolism.
Why does a boiled potato disk barely react with hydrogen peroxide?
Boiling denatures the catalase enzyme — the heat breaks the bonds that hold its molecular shape together. An enzyme's shape determines whether it can grip its target molecule, so a denatured enzyme can no longer break down hydrogen peroxide effectively, even though the potato tissue still looks the same.
What is the dependent variable in the catalase enzyme lab?
It's typically either the time it takes for visible bubbling to start, or the height of foam produced within a fixed time window — both are ways of measuring how fast the enzyme reaction is happening.