30 questions · 30 marks · ≈ 30 min
Which statements would be true regarding the action of all enzyme inhibitors?
| 1 | bind to the active site of an enzyme |
|---|---|
| 2 | cause a change in the tertiary structure of an enzyme |
| 3 | reduce the rate of an enzyme catalysed reaction |
Choose your answer
1, 2 and 3
1 and 2 only
2 and 3 only
3 only
Hyperthermophiles grow optimally at temperatures between 80 and 110°C and comprise of species from both the bacterial and archaeal domains. These organisms have been isolated from all types of terrestrial and marine hot environments, including natural and man-made environments.
Which graph would represent the relationship between temperature and the rate of enzyme activity in hyperthermophiles?
Choose your answer
How does increasing substrate concentration affect the rate of an enzyme-catalysed reaction in the presence of a competitive inhibitor?
Choose your answer
The rate of the reaction slows.
The rate of the reaction increases.
The rate of the reaction slows initially and then recovers.
The rate of the reaction is not affected by additional substrate.
Inhibitors of enzyme reactions form enzyme / inhibitor complexes.
Which statements about enzyme inhibition are correct?
| 1 | The initial rate of reaction is decreased. |
|---|---|
| 2 | The active site changes shape while forming the enzyme/inhibitor complex. |
| 3 | The inhibition can be competitive or non-competitive. |
| 4 | The maximum rate of reaction (Vmax) is increased. |
Choose your answer
1 and 3 only
2 and 3 only
1, 2 and 3 only
2, 3 and 4 only
Pepsin is a digestive enzyme present in the stomach of humans. The stomach environment has a pH of 2.5. Pepsin is most active in acidic environments between pH 1.5 to 2.5. The optimum temperature of pepsin is between 37°C and 42°C.
Which of the following statements is not true?
Choose your answer
Raising the pH of the stomach will decrease pepsin activity.
Above 42°C the bonds in pepsin begin to break.
Above pH 2.5 the tertiary structure of pepsin is changed.
Temperatures below 37°C result in more enzyme/substrate complex being formed.
Which properties are characteristic of a competitive inhibitor of an enzyme?
| binds | effect of adding more substrate | |
|---|---|---|
| A | at active site | reduces inhibition |
| B | at active site | does not reduce inhibition |
| C | at allosteric site | reduces inhibition |
| D | at allosteric site | does not reduce inhibition |
Choose your answer
The Vmax is the rate of reaction when the enzyme is saturated with substrate. This graph shows the effect of increasing substrate on enzyme activity.
What mass of substrate is equal to the ½ Vmax?
Choose your answer
50g
150g
250g
350g
Enzymes can be immobilised in various ways. The diagram below shows two different ways of immobilisation
Immobilised lactase enzymes can be used to make milk digestible for lactose intolerant people. Which of the following statements about the milk produced by the use of immobilised lactase enzymes is not correct?
Choose your answer
The milk would contain glucose and galactose monosaccharides
The milk would taste sweeter and be easier to digest
The milk would contain lactase enzymes
The milk would look the same as regular milk
The graph shows the effect of substrate concentration on the rate of an enzyme-controlled reaction. The enzyme concentration is constant.
Which statement about the graph is correct?
Choose your answer
Between X and Z the temperature is limiting
Between X and Z, the number of enzyme molecules is limiting
Between X and Y, the number of substrate molecules is limiting
Between Y and Z, the number of substrate molecules is limiting
The graph below shows the effect of pH on the rate on three different enzyme-controlled reactions. The enzyme concentration is constant.
Which statement about the graph is not true?
Choose your answer
At its optimum pH, enzyme Y has the fastest rate.
There is no pH at which both Y and Z have a functional active site.
There is no pH at which both X and Z have a functional active site.
There is no pH at which both X and Y have a functional active site.
The graph shows the rate of glucose production with increasing concentration of maltase.
To get a graph with a linear correlation like this which procedure would not be necessary?
Choose your answer
ensure temperature remained constant
ensure there is sufficient maltose availability
ensure pH remained constant
ensure there is sufficient glucose availability
This diagram shows a metabolic pathway.
What would be the effect of adding a competitive inhibitor of enzyme z?
Choose your answer
intermediate 2 would increase in concentration
enzyme z would be denatured
no more end product would be made
rate of reaction of enzyme x would slow
This graph shows the effect of temperature on enzyme activity
Which statement is not true?
Choose your answer
At W the kinetic energy of the substrate is highest
At R the enzyme is completely denatured
At W the rate of enzyme/substrate formation is the highest
At E bonds in the enzyme have started to break
This graph shows the effect of increasing substrate on enzyme activity
What is the Km value?
Choose your answer
50g
250g
350g
500g
Enzymes can be immobilised in various ways. The diagram below shows two different ways of immobilisation
Immobilised lactase enzymes are used to make milk digestible for lactose intolerant people. A student carried out an investigation to compare the activity of the enzyme lactase that had been immobilised in the two different ways shown.
A solution containing 50 mg cm–3 of lactose was poured through a column containing the immobilised enzyme. The solution containing the products was collected and the concentration of glucose measured.
What is the independent variable for this experiment?
Choose your answer
The amount of lactose in the solution before pouring through the column.
The amount of glucose in the milk after pouring through the column.
The type of enzyme immobilization.
The temperature of the solution.
In the graph, Z represents the rate of an enzyme reaction under optimal conditions and without an inhibitor.
Which curve would represent the same experiment carried out in the presence of a low concentration of competitive inhibitor?
Choose your answer
The graph shows the effect of enzyme concentration on the rate of an enzyme-controlled reaction. The substrate concentration is constant.
Which statement about the graph is correct?
Choose your answer
Between X and Z the number of enzyme molecules is limiting
Between Y and Z, the number of enzyme molecules is limiting
Between X and Z, the number of substrate molecules is limiting
Between Y and Z, the number of substrate molecules is limiting
The graph shows the effect of pH on the rate on three different enzyme-controlled reactions. The enzyme concentration is constant.
Which statement about the graph is correct?
Choose your answer
At its optimum pH, enzyme Z has the fastest rate
There is no pH in which both X and Y have a functional active site
Enzyme X has a functional active site across the widest range of pH’s
Enzyme Y has a functional active site across the narrowest range of pH’s
The graph shows the course of an enzyme-catalysed reaction at 25 °C.
Which statement about the graph is incorrect?
Choose your answer
At X the number of available substrate molecules is high
At X the number of enzyme/substrate complexes is the same as Y
At Z the number of available substrate molecules is low
At Y the number of enzyme/substrate complexes is the same as Z
The graph shows the course of two enzyme-catalysed reaction at 30 °C. The only thing that was changed between experiment 1 and 2 was some additional substrate was added at the beginning of experiment 2
Which statement about the experiment is not true?
Choose your answer
At X the number of enzyme/substrate complexes is the same in both 1 and 2
At X the limiting factor in both experiment 1 and 2 is enzyme availability
At Z there are still enzyme/substrate complexes forming in experiment 2
At Y there are no more enzyme/substrate complex forming in experiment 1
The graphs show the rate of reaction of an enzyme-catalyzed reaction.
Which graph shows the effect of increasing the concentration of the substrate both with and without a competitive inhibitor?
Choose your answer
Question 22 - CIE IAS 3.2 Factors that Affect Enzyme Action - HARD
This diagram shows a metabolic pathway occurring in an organelle. The speed of this metabolic pathway is self-regulating as the end product acts as a competitive inhibitor to enzyme 2
What would you not expect to occur when adding additional end product to the organelle?
Choose your answer
enzyme 2 activity would decrease
amount of intermediate Y would decrease
amount of reactant would increase
amount of intermediate X would increase
Ethylene glycol is a colourless and odourless type of alcohol found in many household products. People sometimes drink ethylene glycol mistakenly (or on purpose as a substitute for ethanol), however drinking it can cause profound shock, organ failure, and even death.
Ethylene glycol itself is not toxic, rather the products it gets broken down into. The same enzyme in the body that normally breaks down ethanol into harmless products is also responsible for the hydrolysis of ethylene glycol. This is due to ethylene glycol having a similar structure to ethanol. Accordingly, the treatment for someone who has ingested ethylene glycol is a large dose of ethanol.
Which statement explains why this unusual treatment works?
Choose your answer
Ethanol binds near the active site on the enzyme and alters its shape
Ethanol denatures the enzyme
Ethanol is more likely to bind to the active site of the enzyme
Ethanol acts as a pain killer
Km is the concentration of substrate which permits the enzyme to achieve half Vmax. An enzyme with a high Km requires a greater concentration of substrate to achieve Vmax.
Which of the following statements is correct?
Choose your answer
Enzyme 1 has the lower Km and therefore a greater affinity to its substrate
Enzyme 1 has the higher Km and therefore a greater affinity to its substrate.
Enzyme 2 has the lower Km and therefore a greater affinity to its substrate.
Enzyme 2 has the higher Km and therefore a greater affinity to its substrate.
The curve Z shows the activity of catalase at 25 °C. Curves A,B, C and D show the effect of different conditions on the activity of catalase.
Which curve shows the effect of increasing the temperature by 10 °C and adding additional substrate?
Choose your answer
Enzymes can be immobilized in various ways. The diagram below shows two different ways of immobilization:
Immobilised lactase enzymes are used to make milk digestible for lactose intolerant people. A student carried out an investigation to compare the activity of the enzyme lactase that had been immobilised in the two different ways shown.
A 500 cm3 solution containing 50 mg cm–3 of lactose was poured through a column containing the immobilised enzyme. The solution containing the products was collected and the concentration of glucose measured.
The student collected the following data:
| method of immobilisation | ||
|---|---|---|
| A | B | |
| time for solution to pass through column / seconds | 36 | 28 |
| glucose concentration of end solution / mg cm–3 | 20 | 14 |
What was the rate of glucose production in method A in mg cm–3 min-1 rounded to two significant figures?
Choose your answer
33
33.33
0.55
0.56
In the graph, Z represents the relationship between the initial rate of reaction of an enzyme and the concentration of its substrate under optimal conditions and without an inhibitor.
Which curve would represent the same experiment carried out in the presence of a low concentration of a non-competitive inhibitor?
Choose your answer
The graph shows the effect of substrate concentration on the rate of an enzyme-controlled reaction. The enzyme concentration is constant.
Which statement about the graph is correct?
| Between X and Y | Between Y and Z | |
|---|---|---|
| A | Enzyme is limiting rate | Enzyme is limiting rate |
| B | Enzyme is limiting rate | Substrate is limiting rate |
| C | Substrate is limiting rate | Enzyme is limiting rate |
| D | Substrate is limiting rate | Substrate is limiting rate |
Choose your answer
Km is the concentration of substrate which permits the enzyme to achieve half Vmax.
Which of the following statements is incorrect?
Choose your answer
Enzyme 2 has a greater affinity for its substrate than enzyme 1
Enzyme 1 reaches its Vmax
The Km value of enzyme 2 is greater than the Km value of enzyme 1
The Vmax value of enzyme 2 is greater than the Vmax value of enzyme 1
Immobilised lactase enzymes are used to make milk digestible for lactose intolerant people. A student carried out an investigation to compare the activity of the enzyme lactase that had been immobilised in the two different ways shown below:
A 500 cm3 solution containing 50 mg cm–3 of lactose was poured through a column containing the immobilised enzyme. The solution containing the products was collected and the concentration of glucose measured:
| method of immobilisation | ||
|---|---|---|
| A | B | |
| time for solution to pass through column / seconds | 36 | 28 |
| glucose concentration of end solution / mg cm–3 | 2.0 | 1.4 |
| rate of glucose production / mg sec-1 | 0.055 | 0.05 |
Assuming the mass of glucose is equal to half the initial lactose concentration (i.e. 1 mg of glucose indicates the hydrolysis of 2 mg of lactose), how much lactose could be hydrolysed by method B in an hour with unlimited starting solution?
Choose your answer
180 mg
360 mg
1.4 mg
2.8 mg