Catalase is an enzyme found in many different tissues in plants and animals. It speeds up the rate of the following reaction. hydrogen peroxide water + oxygen Figure 1 shows a 25-day-old broad bean seedling.Some students investigated whether different parts of bean seedlings contained different amounts of catalase. The students: • put hydrogen peroxide into five test tubes • added a different part of a bean seedling to each tube • recorded the results after half a minute. If there was catalase in part of the seedling, oxygen gas was given off. When oxygen gas is given off, foam is produced in the tubes. 5. Page 10 of 19the coronary arteries become narrower as they become filled with fat that lines thewalls of the arteries which leads to higher blood pressure as well as the risk of a heart attack if the artery becomes complety blockedFigure 2 shows the results.The students made the following conclusions: • most parts of a bean seedling contain catalase • the seed contains a lot of catalase • stems and roots have quite a lot of catalase • the leaves have a little bit of catalase • the seed coat has hardly any catalase. The students’ teacher said that the students needed to improve their investigation in order to make valid conclusions. Page 11 of 19(a) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. Describe how you would carry out an investigation to compare the amounts of catalase in different parts of bean seedlings. You should include details of how you would make sure your results give a valid comparison of the amounts of catalase. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (6) (b) Scientists investigated the effect of pH on the activity of the enzyme catalase in a fungus. The table below shows the scientists’ results.pH Enzyme activity in arbitrary units Test 1 Test 2 Test 3 Test 4 Test 5 Mean 3.0 0 0 0 0 0 0 4.0 6 5 8 4 7 6 5.0 38 65 41 42 39 5.5 80 86 82 84 88 84 6.0 100 99 96 103 102 100 6.5 94 92 90 93 91 92 7.0 61 63 61 62 63 62 8.0 22 22 21 24 21 22 Page 12 of 19(i) Calculate the mean enzyme activity at pH 5.0. ______________________________________________________________ ______________________________________________________________ Mean = _____________ arbitrary units (2) (ii) On the graph paper in Figure 3, draw a graph to show the scientists’ results. Remember to: • add a label to the vertical axis • plot the mean values of enzyme activity • draw a line of best fit. Figure 3(4) (iii) At what pH does the enzyme work best? ____________________ (1) Page 13 of 19(iv) Predict the activity of the enzyme at pH 9.0. ____________________ arbitrary units (1) (v) Suggest why the enzyme’s activity at pH 3.0 is zero. ______________________________________________________________ ______________________________________________________________ (1)
Question
Catalase is an enzyme found in many different tissues in plants and animals. It speeds up the rate of the following reaction. hydrogen peroxide water + oxygen Figure 1 shows a 25-day-old broad bean seedling.Some students investigated whether different parts of bean seedlings contained different amounts of catalase. The students: • put hydrogen peroxide into five test tubes • added a different part of a bean seedling to each tube • recorded the results after half a minute. If there was catalase in part of the seedling, oxygen gas was given off. When oxygen gas is given off, foam is produced in the tubes. 5. Page 10 of 19the coronary arteries become narrower as they become filled with fat that lines thewalls of the arteries which leads to higher blood pressure as well as the risk of a heart attack if the artery becomes complety blockedFigure 2 shows the results.The students made the following conclusions: • most parts of a bean seedling contain catalase • the seed contains a lot of catalase • stems and roots have quite a lot of catalase • the leaves have a little bit of catalase • the seed coat has hardly any catalase. The students’ teacher said that the students needed to improve their investigation in order to make valid conclusions. Page 11 of 19(a) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. Describe how you would carry out an investigation to compare the amounts of catalase in different parts of bean seedlings. You should include details of how you would make sure your results give a valid comparison of the amounts of catalase. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (6) (b) Scientists investigated the effect of pH on the activity of the enzyme catalase in a fungus. The table below shows the scientists’ results.pH Enzyme activity in arbitrary units Test 1 Test 2 Test 3 Test 4 Test 5 Mean 3.0 0 0 0 0 0 0 4.0 6 5 8 4 7 6 5.0 38 65 41 42 39 5.5 80 86 82 84 88 84 6.0 100 99 96 103 102 100 6.5 94 92 90 93 91 92 7.0 61 63 61 62 63 62 8.0 22 22 21 24 21 22 Page 12 of 19(i) Calculate the mean enzyme activity at pH 5.0. ______________________________________________________________ ______________________________________________________________ Mean = _____________ arbitrary units (2) (ii) On the graph paper in Figure 3, draw a graph to show the scientists’ results. Remember to: • add a label to the vertical axis • plot the mean values of enzyme activity • draw a line of best fit. Figure 3(4) (iii) At what pH does the enzyme work best? ____________________ (1) Page 13 of 19(iv) Predict the activity of the enzyme at pH 9.0. ____________________ arbitrary units (1) (v) Suggest why the enzyme’s activity at pH 3.0 is zero. ______________________________________________________________ ______________________________________________________________ (1)
Solution
(a) To carry out an investigation to compare the amounts of catalase in different parts of bean seedlings, I would follow these steps:
- Collect several bean seedlings of the same age and grown under the same conditions to ensure consistency.
- Separate the seedlings into their different parts: seeds, stems, roots, leaves, and seed coats.
- Crush each part separately using a mortar and pestle to break down the cell walls and release the enzymes.
- Add the same volume of hydrogen peroxide to each crushed part in separate test tubes. The hydrogen peroxide serves as the substrate for the catalase.
- Immediately after adding the hydrogen peroxide, place a gas syringe or a manometer on top of each test tube to measure the amount of oxygen gas produced.
- Record the volume of oxygen gas produced after a set amount of time (e.g., 30 seconds) for each test tube.
- Repeat the experiment several times to ensure reliability and calculate the average volume of oxygen gas produced for each part of the seedling.
This method ensures a valid comparison of the amounts of catalase because the same volume of hydrogen peroxide is used for each part, the reaction time is controlled, and the age and growing conditions of the seedlings are consistent.
(b) (i) To calculate the mean enzyme activity at pH 5.0, add up the enzyme activity values and divide by the number of tests. (38 + 65 + 41 + 42 + 39) / 5 = 45 arbitrary units.
(ii) For the graph, label the vertical axis as "Enzyme Activity (arbitrary units)". Plot the mean values of enzyme activity against the pH values. Draw a line of best fit through the points.
(iii) The enzyme works best at pH 6.0, as this is where the mean enzyme activity is highest.
(iv) It's difficult to predict the activity of the enzyme at pH 9.0 without further data, but based on the trend, it would likely be lower than at pH 8.0.
(v) The enzyme's activity at pH 3.0 is zero because the acidic environment denatures the enzyme, changing its shape so it can no longer bind to its substrate and carry out its function.
Similar Questions
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Scientists investigated the effect of pH on the activity of the enzyme catalase in a fungus. The table below shows the scientists’ results.pH Enzyme activity in arbitrary units Test 1 Test 2 Test 3 Test 4 Test 5 Mean 3.0 0 0 0 0 0 0 4.0 6 5 8 4 7 6 5.0 38 65 41 42 39 5.5 80 86 82 84 88 84 6.0 100 99 96 103 102 100 6.5 94 92 90 93 91 92 7.0 61 63 61 62 63 62 8.0 22 22 21 24 21 22 Page 12 of 19The independent variables are the different parts of the bean seedling.The dependent variable is the amount of catalyst used The control variables are the temperature, concentration of hydrogen peroxide and the time for the investigationfirst get fresh bean seedling of the same age and sizethen get 5 test stubes labelled for each part of the bean seedling: seed, stem, root, leaf and seed coat and add the same volume of hydrogen peroxide to each test tube (25cm^3). Keep a separate 6th test tube with only hydrogen peroxide to compare against.cut a standardized piece of each part of the bean seedling seed, stem, root, leaf and seed coat and add them to their retrospective test tube.Observe and record the production of oxygen gas (which will be indicated by the amount of foam produced) after a certain time e.g. 30 seconds measure the height and volume of the foam and record it for each test tubeCompare the amount of foam produced for each test tube and that tells us the amounts of catalyst in the different parts of the bean seedling(i) Calculate the mean enzyme activity at pH 5.0. ______________________________________________________________ ______________________________________________________________ Mean = _____________ arbitrary units (2) (ii) On the graph paper in Figure 3, draw a graph to show the scientists’ results. Remember to: • add a label to the vertical axis • plot the mean values of enzyme activity • draw a line of best fit. Figure 3(4
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