A student investigated the decomposition of hydrogen peroxide. They compared the reaction with yeast extract (which contains the enzyme catalase) to the reaction without yeast extract. They measured the volume of oxygen gas produced over a period of 120 seconds.

Their results are shown in the graph below.

![A line graph with 'Volume of oxygen produced (cm³)' on the vertical y-axis from 0 to 50, and 'Time (seconds)' on the horizontal x-axis from 0 to 120. There are two curves:

1. 'With yeast extract' starts at (0,0), rises very steeply, and levels off (plateaus) at 40 cm³ at 80 seconds.
2. 'Without yeast extract' is a flat line along the x-axis, remaining at 0 cm³ from 0 to 120 seconds.](https://assets.mathsgenie.co.uk/aqa-qb/e1c3ddc0-0c97-403e-ad75-aa616e3ddbe7.png)