Catalase enzyme lab
01 // Question
How does reaction temperature relate to bubble-start time and foam height in a potato-catalase test?
Keep the peroxide and potato sample at the same measured condition, then change only temperature across the three groups.
02 // Variables
Independent
Starting temperature of the reaction mixture- Cold bath (about 5–10 °C)
- Room temperature (measure it)
- Comfortably warm bath (about 35–40 °C)
Dependent
Time until first clear bubbles and foam height after 60 seconds- Seconds until first clear bubbles
- Foam height at exactly 60 seconds (mm)
03 // Hypothesis
IF the potato and peroxide begin at a comfortably warm rather than cold temperature, THEN the first clear bubbles may appear sooner under these tested conditions, BECAUSE temperature can change enzyme reaction rate, but the result depends on the range and the actual potato; excessive heat can alter enzyme structure.
04 // Procedure
1. Prepare nine matched disks
Cut nine fresh potato disks with the same diameter and thickness. Use a tray and adult help with cutting tools.
2. Set three reaction temperatures
Set up cold (about 5–10 °C), measured room-temperature, and comfortably warm (about 35–40 °C) water baths. Keep the warm bath below 40 °C.
3. Equilibrate matched samples
For each independent trial, place one disk in a dry labeled cup and 15 mL of 3% peroxide in an identical open reaction cup. Let both reach that condition in the same bath for about five minutes; record the actual starting temperature.
4. Run three fresh trials per condition
Move one disk into its matching peroxide cup and start timing at contact. Record seconds to first clear bubbles; if none appear by 60 seconds, record ‘not observed by 60 s.’ Repeat with a fresh disk and peroxide portion for all nine trials.
5. Measure and compare
At exactly 60 seconds, measure foam height in millimeters. For each temperature, keep all three readings and compare the mean and range for both outcomes.
Materials // Prepare the bench
- Potato
- 3% hydrogen peroxide
- nine identical open cups
- water-bath cups
- cork borer or adult-handled cutter
- ruler
- timer
- thermometer
- tray
- splash goggles
05 // Data table
| Reaction temperature / trial | Starting temp (°C) | First bubbles (s; or not seen by 60 s) | Foam at 60 s (mm) |
|---|---|---|---|
| Cold · 1 | ____ | ____ | ____ |
| Cold · 2 | ____ | ____ | ____ |
| Cold · 3 | ____ | ____ | ____ |
| Room · 1 | ____ | ____ | ____ |
| Room · 2 | ____ | ____ | ____ |
| Room · 3 | ____ | ____ | ____ |
| Warm · 1 | ____ | ____ | ____ |
| Warm · 2 | ____ | ____ | ____ |
| Warm · 3 | ____ | ____ | ____ |
Formula Keep every trial visible. Calculate mean and range for bubble-start time only when all three trials have an observed start; if any has no clear bubbles by 60 s, report that count and the observed times without treating a non-observation as 60 s. Calculate foam-height mean and range from the three 60-second readings.
06 // What to expect
A comfortably warm reaction may show earlier bubbles than a cold one, but results depend on the actual starting temperatures, potato tissue and procedure. Use the three independent trials at each condition rather than assuming the order.
This comparison does not test boiling or locate a temperature optimum. Keep the warm bath at or below 40 °C; very high heat can alter enzyme structure and reduce activity.
07 // Lab notes
- Use one fresh potato disk and a fresh peroxide portion for every trial. Never use concentrated peroxide.
- Keep every reaction container open on a tray so oxygen can escape. Do not use a flame or seal a vessel.
08 // Remember
Catalase releases oxygen as it breaks down hydrogen peroxide. Compare three independent trials per temperature; this test does not locate an exact optimum.
09 // Connect catalase to the reaction
Potato tissue contains catalase, which speeds the decomposition 2 H₂O₂ → 2 H₂O + O₂. The visible bubbles are oxygen. This procedure does not add dish soap: foam can still form, but its height depends on bubble size, drainage, cup shape, and the potato surface as well as oxygen production. Bubble-start time and 60-second foam height are separate indicators; neither directly measures gas volume or enzyme molecules.
Match disk diameter and thickness, use the same potato when possible, and keep every cup open. The tested factor is starting reaction temperature, so equilibrate each dry disk and its 15 mL peroxide portion in the same measured bath before combining them. If only the potato is cooled while peroxide stays at room temperature, the mixture warms at contact and the temperature treatment is unclear.
10 // Interpret enzyme activity without assuming it rises forever
Prepare nine equal fresh disks and nine 15 mL portions of 3% household hydrogen peroxide. Use three separate open cups for each condition: cold (about 5–10 °C), room temperature (measure it), and comfortably warm (about 35–40 °C). Keep the warm bath at or below 40 °C. Let each dry disk and its matching peroxide cup equilibrate for about five minutes, record starting temperature, then combine one pair and start timing at contact.
Record seconds to the first clear bubbles and foam height in millimeters at exactly 60 seconds for every trial. Keep all nine raw rows. For each temperature, calculate the mean and range separately for bubble time and foam height. Graph means against measured temperature while keeping individual readings or ranges visible; a mean alone can hide an unusual disk. Three conditions do not establish a universal order or locate an exact optimum.
11 // Handle peroxide and improve repeatability
Wear splash goggles, use adult supervision and only 3% household peroxide. Keep it away from eyes, skin and mouths. Place all open reaction cups on a tray so oxygen can escape; do not taste materials, use a flame, or seal a bubbling vessel. Do not use boiling water or concentrated peroxide. Follow the product label and classroom rinse/cleanup directions if there is a splash.
If results vary, check disk size, potato freshness, actual starting temperature, peroxide volume, contact timing, and cup shape. A no-potato comparison can check for background bubbling, but do not silently subtract it from class readings. A separate extension can compare raw and cooked potato using matched samples; keep that question distinct from the temperature series.
12 // Questions people ask
Why does hydrogen peroxide bubble when it touches a potato?
Potato tissue contains catalase, which speeds the breakdown of hydrogen peroxide into water and oxygen gas. The visible bubbles are oxygen; foam height also depends on bubble stability and is not a direct oxygen-volume measurement.
Why should both the potato and peroxide reach the selected temperature?
If only the potato is chilled or warmed while peroxide stays at room temperature, the mixture temperature changes when they are combined. Equilibrating both first makes the starting reaction temperatures more comparable; record the actual value.
Why run three trials at each temperature?
Fresh independent trials show how much results vary. Keep all three readings, then compare the mean and range instead of relying on one disk.
What if no clear bubbles appear within 60 seconds?
Record ‘not observed by 60 s’ and still measure foam at exactly 60 seconds. Do not replace a non-observation with a 60-second bubble time; report the number observed and summarize bubble times only when all three trials have an observed onset.
Does this test find catalase's exact optimum temperature?
No. Three classroom conditions show only a limited range and do not locate an exact optimum. Do not boil samples; very high heat can alter an enzyme's structure.
13 // Keep going
Can you explain the investigation?
Catalase enzyme lab · Student Data Sheet
Question: How does reaction temperature relate to bubble-start time and foam height in a potato-catalase test?
Hypothesis: If the potato and peroxide begin at a comfortably warm rather than cold temperature, then the first clear bubbles may appear sooner under these tested conditions, because temperature can change enzyme reaction rate, but the result depends on the range and the actual potato; excessive heat can alter enzyme structure.
Materials
- Potato
- 3% hydrogen peroxide
- nine identical open cups
- water-bath cups
- cork borer or adult-handled cutter
- ruler
- timer
- thermometer
- tray
- splash goggles
Safety before starting
- Wear splash goggles and use adult supervision with 3% household hydrogen peroxide only. Never use concentrated peroxide; keep it off skin and out of eyes and mouths.
- Keep the reaction vessel open and on a tray. If solution splashes, stop and follow the product label and the classroom rinse procedure.
Lab notes
- Use one fresh potato disk and a fresh peroxide portion for every trial. Never use concentrated peroxide.
- Keep every reaction container open on a tray so oxygen can escape. Do not use a flame or seal a vessel.
Variables
Independent: Starting temperature of the reaction mixture · Dependent: Time until first clear bubbles and foam height after 60 seconds
Keep constant: same potato and disk dimensions · 3% peroxide and 15 mL per trial · matched peroxide/disk starting temperature · same open container and timing rule · three fresh independent trials per condition
Procedure
- Prepare nine matched disks: Cut nine fresh potato disks with the same diameter and thickness. Use a tray and adult help with cutting tools.
- Set three reaction temperatures: Set up cold (about 5–10 °C), measured room-temperature, and comfortably warm (about 35–40 °C) water baths. Keep the warm bath below 40 °C.
- Equilibrate matched samples: For each independent trial, place one disk in a dry labeled cup and 15 mL of 3% peroxide in an identical open reaction cup. Let both reach that condition in the same bath for about five minutes; record the actual starting temperature.
- Run three fresh trials per condition: Move one disk into its matching peroxide cup and start timing at contact. Record seconds to first clear bubbles; if none appear by 60 seconds, record ‘not observed by 60 s.’ Repeat with a fresh disk and peroxide portion for all nine trials.
- Measure and compare: At exactly 60 seconds, measure foam height in millimeters. For each temperature, keep all three readings and compare the mean and range for both outcomes.
Record your observations
| Reaction temperature / trial | Starting temp (°C) | First bubbles (s; or not seen by 60 s) | Foam at 60 s (mm) |
|---|---|---|---|
Formula: Keep every trial visible. Calculate mean and range for bubble-start time only when all three trials have an observed start; if any has no clear bubbles by 60 s, report that count and the observed times without treating a non-observation as 60 s. Calculate foam-height mean and range from the three 60-second readings.
Answer key and expected pattern
A comfortably warm reaction may show earlier bubbles than a cold one, but results depend on the actual starting temperatures, potato tissue and procedure. Use the three independent trials at each condition rather than assuming the order.
This comparison does not test boiling or locate a temperature optimum. Keep the warm bath at or below 40 °C; very high heat can alter enzyme structure and reduce activity.
Remember: Catalase releases oxygen as it breaks down hydrogen peroxide. Compare three independent trials per temperature; this test does not locate an exact optimum.