1 markThe effect of pH on the rate of reaction of three different enzymes is shown in the graph below.
What does the graph show?
Each enzyme works best over a narrow temperature range.
Most enzymes work best around a neutral pH.
Enzymes work better in acidic conditions.
Each enzyme works best at a different pH.
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1 markLiver cells produce an enzyme called catalase which breaks down toxic hydrogen peroxide into water and oxygen.
A student set up an experiment where cubes of cows' liver in a test tube were incubated with hydrogen peroxide at different temperatures.
The student counted the number of bubbles of oxygen released per minute at each temperature.
Their results are shown in the table below:
| temperature / oC | 10 | 20 | 30 | 40 | 50 |
| number of bubbles / minute | 35 | 68 | 79 | 63 | 5 |
The results suggest that the optimum temperature for catalase is between which two values?
10°C and 40°C
20°C and 30°C
30°C and 40°C
20°C and 40°C
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1 markStarch is digested by the enzyme amylase. Four identical mixtures of starch and amylase were kept at different temperatures.
The graph below shows the time taken for the starch to be digested at each temperature.
At which temperature is the rate of reaction highest?
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1 markWhich graph in the image below shows the correct effect of temperature on the activity of an enzyme?
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1 markThe pH of an enzyme controlled reaction is decreased by a pH of 2.
How does this affect the rate of the reaction?
It has no effect on the rate.
It always decreases the rate.
It always increases the rate.
It may increase or decrease the rate .
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1 markTemperature affects the rate of all enzyme-controlled reactions, as shown in the graph below.
Which row correctly describes what is happening at the points on the graph?
| X | Y | |
| A | the enzyme has been denatured | the rate of reaction is decreasing |
| B | the rate of reaction is increasing | the enzyme is becoming denatured |
| C | the reaction is taking less time | the rate of reaction is increasing |
| D | the rate of reaction is decreasing | the enzyme is becoming denatured |
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1 markA student decided to investigate the effect of pH on the activity of the enzyme lipase.
Five different test tubes are set up. Each test tube contains a mixture of the enzyme lipase and its substrate, a lipid.
Which condition should not be kept the same in each of the five test tubes?
Temperature
Concentration of lipase
Volume of lipid solution
pH
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1 markWhich of the following correctly describes the effect of increasing temperature from 15°C to 30°C on an enzyme-controlled reaction?
| kinetic energy of enzymes and substrates | frequency of effective collisions | shape of active site | |
| A | no change | decreases | denatured |
| B | increases | increases | denatured |
| C | increases | increases | no change |
| D | decreases | no change | no change |
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