Measure reaction progress with catalase
Catalase progress can be followed by measuring oxygen product formation over time under controlled conditions.
AS Level · Cambridge International Biology 9700, 2028–2030. These lessons teach enzyme concepts and experimental reasoning. Written practice is self-checked; it does not demonstrate supervised practical competence or replace teacher-reviewed assessment.
Before you begin
- Recognise that proteins have specific three-dimensional shapes and that reaction rates can be compared using controlled measurements.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which product can be measured to follow catalase reaction progress?
What you will learn
- Describe a way to follow catalase-catalysed reaction progress
- Calculate a rate of product formation from measurements over time
Follow oxygen as a product
Catalase catalyses the breakdown of hydrogen peroxide, producing water and oxygen. Reaction progress can be followed by measuring oxygen formed over time, for example with a gas syringe in a suitable supervised setup.
Take readings at stated time intervals and use the same starting volume and concentration of substrate, enzyme amount, temperature and pH when comparing trials. Keep the apparatus sealed appropriately and check that it does not leak.
Calculate and interpret rate
A rate over an interval can be calculated as change in product amount or volume divided by elapsed time. The initial rate uses the earliest linear part of a progress record, before substantial substrate depletion or product effects.
Repeat measurements and calculate a mean when appropriate. A gas-syringe volume is an operational measure of oxygen collected; leaks, delayed mixing, temperature changes and gas dissolving can affect the reading. Written planning does not demonstrate practical skill.
Pause and explain
How is a mean product-formation rate calculated?
Worked example
A catalase reaction produces 18 cm³ of oxygen in 30 s. Calculate the mean rate over this interval.
Show the worked solution
- Use product volume divided by time.
- 18 ÷ 30 = 0.60 cm³ s⁻¹.
Answer Mean rate = oxygen formed ÷ time = 18 cm³ ÷ 30 s = 0.60 cm³ s⁻¹. This is the mean over the full 30 s, not necessarily the initial rate.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
State one direct measurement that can follow catalase reaction progress.
Give me a hint
Measure the formation of a product.
Compare my reasoning
- Catalase produces oxygen from hydrogen peroxide.
- Collect and measure oxygen volume over time.
Measure the volume of oxygen formed at recorded time intervals, for example using a suitable gas-collection apparatus.
Look for these in your work
- Product identified
- Measurement made over time
A trial produces 12 cm³ oxygen in 20 s; a second produces 21 cm³ in 35 s. Calculate each mean rate.
Give me a hint
Divide each oxygen volume by its own time.
Compare my reasoning
- 12 ÷ 20 = 0.60 cm³ s⁻¹.
- 21 ÷ 35 = 0.60 cm³ s⁻¹.
Trial 1: 12 ÷ 20 = 0.60 cm³ s⁻¹. Trial 2: 21 ÷ 35 = 0.60 cm³ s⁻¹. The mean rates over the stated intervals are equal.
Look for these in your work
- Both calculations correct
- Rate units included
A gas syringe shows little oxygen for the first five seconds, then a rapid increase. Give one reason for an early delay and one way to improve the timing.
Give me a hint
Think about mixing and when timing begins.
Compare my reasoning
- The enzyme and substrate may not mix immediately.
- Start the timer as soon as the reaction mixture is combined using a consistent method.
The early delay could result from slow or inconsistent mixing, or from starting the timer after the reaction begins. Combine the solutions quickly and start timing at a clearly defined point using the same method for each repeat.
Look for these in your work
- Plausible delay identified
- Consistent timing improvement proposed
Common mistakes
- Measuring substrate disappearance when asked to measure catalase product formation
- Calling a full-interval mean the initial rate
- Comparing trials that differ in temperature or enzyme amount as well as the intended variable
What can you explain now?
Which product can be measured to follow catalase reaction progress?
Compare with the explanation
Oxygen
Catalase breakdown of hydrogen peroxide produces oxygen.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Make it stick
How can catalase progress be measured, and what is the difference between mean and initial rate?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.