NEW
Font size
WorksheetsAS Biology Cambridge - Chap 3
Total questions: 20
Worksheet time: 12mins
The graph shows the activity of an enzyme at different temperatures. What does the dashed line in the graph represent?
Increasing temperature increases substrate concentration
Increasing temperature affects the active site
Increasing temperature increases the rate of reaction
Increasing temperature decreases the movement of particles
The graph shows the effect of changing the substrate concentration on the early stages of an enzyme-catalysed reaction. What can be interpreted about the rate of reaction from the graph ?
Rate of reaction increases up to a point and then remains constant
Rate of reaction increases linearly with increasing substrate concentration
Rate of reaction increases non-linearly with increasing substrate concentration
Rate of reaction is not affected by any change in the substrate concentration
In an experiment the effect of changing pH on an enzymatic reaction is tested. Which could be a dependent variable in this kind of experiment?
Changing substrate concentration
Rate of formation of product
Variation in temperature
Change in pH
In one of the curves in the graph, the rate of an enzyme-catalysed reaction has been plotted against the substrate concentration in presence of a small quantity of a competitive inhibitor. Which curve represents competitive inhibition?
A
B
C
D
Which is the activation energy of a reaction when it is catalysed by an enzyme?
A
B
C
D
Enzyme activity has been measured for two enzymes at different pH values. At which pH is one enzyme optimal and the other enzyme denatured?
pH = 5
pH = 6
pH = 8
pH = 10
In enzyme experiments, the rate of enzyme activity often gradually decreases. What is most likely to cause this decrease?
The temperature decreasing
The enzyme concentration decreasing
The pH decreasing
The substrate concentration decreasing
Which graph shows the effect of increasing substrate concentration on enzyme activity?
For what purpose is the enzyme lactase useful?
Production of lactose-free milk so that more people can consume dairy products
As a dietary supplement to aid in protein digestion of milk
For use in coagulating milk protein to make cheese
To improve protein consumption in developing countries that lack milk
Which graph shows the effect of increasing the substrate concentration on enzyme activity?
The graph shows how the rate of an enzyme-catalysed reaction depends on the concentration of substrate. What is the Michaelis-Menten constant (Km) for this enzyme under these conditions?
0.19 mmol dm–3
0.38 mmol dm–3
1.5 mmol dm–3
5.0 mmol dm–3
In an investigation, the same concentration of the enzyme phosphorylase was added to different concentrations of glucose phosphate and incubated at 30 °C. At 1 minute intervals, one drop of the reaction mixture was removed and added to a drop of iodine solution on a white tile. The diagram shows the results of this investigation.What explains the trend in the results of this investigation?
Phosphorylase catalyses a reaction converting glucose phosphate to starch.
The maximum rate of reaction is reached at 20 mg dm–3 of glucose phosphate.
Substrate concentration is limiting at concentrations of glucose phosphate 25 mg dm–3 or less
Enzyme concentration is limiting at concentrations of glucose phosphate 25 mg dm–3 or less.
What is the definition of the Michaelis-Menten constant, Km, for an enzyme?
Vmax
half Vmax
the substrate concentration that gives Vmax
the substrate concentration that gives half Vmax
A fixed volume of the enzyme catalase was added to a fixed volume of hydrogen peroxide solution. The diagram shows how the concentration of product changed over the course of the reaction. What explains the shape of this graph?
The active sites become saturated.
The enzyme was denatured.
The hydrogen peroxide inhibited the reaction.
The substrate molecules were used up.
The enzyme β-galactosidase can catalyse the hydrolysis of four substrates, A, B, C and D, with similar structures. Each substrate has a different Km value. For which substrate does β-galactosidase have the lowest affinity?
Km = 4 × 10–3 mol dm–3
Km = 1 × 10–3 mol dm–3
Km = 2 × 10–4 mol dm–3
Km = 1 × 10–4 mol dm–3
Which is correct for competitive inhibitors of enzymes?
1 They occupy the active site of an enzyme.
2 They have exactly the same shape as the substrate.
3 They can be used to control the rate of enzyme activity.
4 They can bind to a site on an enzyme other than the active site.
1,2 and 3
1 and 3
1 only
2,3 and 4
The effect of substrate concentration on an enzyme-catalysed reaction was measured in three different conditions:
● with no inhibitor
● with a competitive inhibitor
● with a non-competitive inhibitor.
The graph shows the results. Which statement is correct?
X is a competitive inhibitor which binds to a site other than the active site of the enzyme.
X is a non-competitive inhibitor which has a similar shape to the active site of the enzyme.
Y is a competitive inhibitor which has a similar shape to the active site of the enzyme.
Y is a non-competitive inhibitor which binds to a site other than the active site of the enzyme.
The graph compares the effect of temperature on the activity of the protease enzyme, papain, when in solution (free) and when immobilised in alginate beads. Which statement about the effect of immobilisation of papain is correct?
It alters the shape of papain’s active site at higher temperatures.
It decreases the activity of papain at higher temperatures.
It increases the stability of papain at higher temperatures.
It reduces the number of collisions of papain with the substrate.
How is the Michaelis-Menten constant (Km) used?
to assess the efficiency of an enzyme in catalysing a reaction
to compare the affinity of enzymes for their substrate
to find the maximum velocity of an enzyme (Vmax)
to find the rate at which substrate is loaded by an enzyme
The following statements are about enzymes.
1 Folding of an enzyme molecule causes the formation of the active site.
2 The shape of the active site changes to enable the substrate to bind.
3 Temporary bonds hold the substrate in the active site.
4 More enzyme-substrate complexes are formed at the optimum temperature.
Which statements are correct for the induced fit hypothesis?
1 and 2
1 and 3
2,3 and 4
2 and 4 only
