Biology 11–12 · Year 11

Catalase and hydrogen peroxide: reaction rate against substrate concentration

Module 1: Cells as the Basis of Life (Cell Function)

Practical, model not builtMedium risk

School laboratory, not for home

In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

This site has no interactive model of its own. Where a step or a material names a Concept Studio model, simulation or tool, it has not been built; an external simulation a step names (for example PhET) is not part of this site.

The idea

The rate of an enzyme-catalysed reaction depends on substrate concentration. Many enzymes level off once their active sites are saturated, but catalase breaks down hydrogen peroxide at a rate proportional to its concentration over the range a school can use.

Safety card

Medium riskA teacher supervises

Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

Hazards

Hydrogen peroxide at 20 and 25 volume is an irritant to eyes and skin; the 30 volume solution is above the source's irritant band of 18 to 28 volume and is more hazardous still, especially to the eyes
Pressure build-up if the delivery tube is obstructed
Foaming may overflow the flask

Controls

Wear eye protection (splash goggles when the 30 volume solution is in use) and cover clothing; wash splashes off at once; the teacher or technician dispenses the 30 volume solution
Ensure the bung is a tight fit and the tube is clear before injecting
Use no more than 2 mL peroxide per run

Note

Hydrogen peroxide handling and concentrations: NSW Department of Education Chemical Safety in Schools package (https://education.nsw.gov.au/content/dam/main-education/asset-management/chemical-safety/1._Section_1_-_General_information_for_all_staff.pdf) and RiskAssess (https://www.riskassess.com.au/).

What you need

Pureed potato (catalase source), 20 mL per run, kept cold
Hydrogen peroxide at 10, 15, 20, 25 and 30 volume strength, 2 mL per run (the source uses these five concentrations)
Conical flask 100 mL with a bung fitted with a delivery tube; 2 mL syringe through the bung
Trough of water; an inverted 50 mL measuring cylinder for the 10, 15 and 20 volume runs and an inverted 100 mL measuring cylinder for the 25 and 30 volume runs, as the source directs for concentrations over 20 volume (2 mL of 25 and 30 volume peroxide can release up to 54.6 and 65.5 mL of oxygen at 25 degrees Celsius; computed); stop clock
Eye protection; lab coat or apron

How to do it

Measure 20 mL pureed potato into the flask, fit the bung and delivery tube, and fill the inverted measuring cylinder of the right size for the run with water in the trough.
Inject 2 mL of 10 volume hydrogen peroxide through the bung and start the clock.
After 30 seconds record the volume of oxygen collected; calculate rate in mL per second.
Rinse the flask and repeat with fresh puree for 15, 20, 25 and 30 volume peroxide, three trials at each concentration.
Plot mean rate against peroxide concentration and describe the shape of the curve.
Further run: heat a portion of the puree to boiling, cool it, and repeat one run to show that a denatured enzyme gives no measurable oxygen.

What you should see

Oxygen is collected within seconds and the rate rises with peroxide concentration, close to in proportion, because catalase decomposes hydrogen peroxide by first-order kinetics, the rate being proportional to the peroxide concentration, and is not saturated at these concentrations. A curve that flattens at the top points to the apparatus, such as oxygen lost before it is collected, foam, or a cylinder too small for the run, or to the peroxide inactivating the enzyme, not to saturated active sites. The upper bound is fixed by stoichiometry: 2 H2O2 gives 2 H2O + O2, and 2 mL of 10 volume peroxide can release at most 20 mL of oxygen at 0 degrees Celsius, about 21.8 mL at 25 degrees Celsius (computed), so a 30 second volume well below this shows the reaction is still in progress. Boiled puree releases no oxygen. The learner knows it worked when replicate rates agree and the plot rises steadily with concentration.

What changes

What you change: hydrogen peroxide concentration (volume strength)
What you measure: volume of oxygen collected in 30 seconds (rate in mL per second)
What you keep the same: mass and batch of potato puree
volume of peroxide
temperature
time before reading
apparatus

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

A curve that levels off always means the active sites are saturated; catalase is not saturated at school peroxide concentrations, so a flattening curve points to lost gas, foam or enzyme inactivation.
The enzyme is used up in the reaction; catalase is unchanged and can be reused.
Boiling makes an enzyme work faster; heat beyond its tolerance denatures it permanently.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Biology Stage 6 Syllabus (2017), current: Year 11 taught to the end of 2026 and Year 12 to Term 3 2027BIO11-8 BIO11/12-3 BIO11/12-4
Biology 11–12 Syllabus (2025), Year 11 focus area Cells as the basis of life; new syllabus not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027BI-11-01
Biology 11–12 Syllabus (2025), Year 11 Working scientifically; new syllabus not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027BI-11WS-03 BI-11WS-04 BI-11WS-05
Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

All Concept Studio activities