A student investigated how the concentration of a yeast suspension affects the activity of the enzyme catalase. Yeast is rich in catalase, which breaks down...
Question 1 Report
A student investigated how the concentration of a yeast suspension affects the activity of the enzyme catalase. Yeast is rich in catalase, which breaks down hydrogen peroxide and releases a gas. The student added the same volume of hydrogen peroxide to each of five test tubes, then added a different concentration of yeast suspension to each tube. A froth of gas bubbles rose up each tube. After one minute she measured the height of the froth with a ruler held against the tube, as shown in Fig. 3.1. The temperature was kept the same throughout. Her results are shown in Table 3.1.
| Concentration of yeast / % | 1 | 2 | 4 | 6 | 8 |
|---|---|---|---|---|---|
| Height of froth after 1 min / mm | 10 | 22 | 38 | 52 | 60 |
(a) Measure, from Table 3.1, the height of the froth produced by the 4% yeast suspension. [1]
(b) Record the yeast concentration that produced the tallest froth. [1]
(c) Describe how the ruler in Fig. 3.1 is used to measure the height of the froth. [2]
(d) Name the gas that forms the froth. [1]
(e) Suggest two variables that must be kept constant. [2]
Answer Details
This enzyme question tests reading a table, correct use of a ruler, identifying the gas, and controlled variables.
(a) From Table 3.1, the 4% yeast suspension produced a froth height of 38 mm [1].
(b) The tallest froth (60 mm) was produced by the 8% yeast suspension [1]; the more concentrated the yeast, the more catalase there is, so more oxygen is released.
(c) To measure the froth with the ruler, stand the ruler upright against the outside of the tube with the zero level with the liquid surface [1], then read the scale at the top of the froth at eye level to avoid parallax error [1].
(d) The gas that forms the froth is oxygen [1] - catalase breaks hydrogen peroxide down into water and oxygen.
(e) Any two variables that must be kept constant: temperature; the volume (or concentration) of hydrogen peroxide; the volume of yeast added; the time left before measuring [2]. Keeping these fixed ensures that only the yeast concentration affects the froth height.
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