WorksheetsFactors and conditions affecting the activity of enzymes
Total questions: 15
Worksheet time: 8mins
Which statements describe some enzyme actions?
1 Enzymes hold reacting molecules so that their reactive groups are close together.
2 In an enzyme-catalysed reaction, more molecules have sufficient energy to react
than in the absence of the enzyme.
3 Reactions catalysed by enzymes take place at a lower temperature than they would
without the enzyme.
1, 2 and 3
1 and 2 only
1 and 3 only
2 and 3 only
In a reaction controlled by an enzyme, which of the following graphs shows the effect of substrate concentration on the rate of the reaction?
A
B
C
D
What determines the specificity of an enzyme?
1 the covalent and other bonding between R groups of the polypeptide
2 the optimum pH of the enzyme
3 the covalent peptide bonds between amino acids of the polypeptide
4 the shape of the substrate molecule
1, 2, 3 and 4
1 and 3 only
1 only
2, 3 and 4 only
Apart from oxygen, what product is made when hydrogen peroxide breaks down?
H2O
СO2
H2O2
SO2
The graph shows the progress of the digestion of starch by the enzyme salivary amylase. Why does the reaction slow down?
End-product inhibition by maltose
The salivary amylase is becoming denatured
The salivary amylase is gradually becoming saturated with starch
There are fewer and fewer substrate molecules left to bind with the salivary amylase
The graph shows the effect of temperature on the rate at which the enzyme in a biological washing powder digests and removes fruit juice stains.
Which statements explain the shape of the graph at temperatures higher than X?
1 Bonds are broken between the R groups of the amino acids in the polypeptide chains of
the enzyme.
2 There are more collisions between the enzyme and its substrate.
3 The tertiary structure of the enzyme is altered.
4 The shapes of the active site and the substrate are no longer complementary.
1, 2 and 3
1, 2 and 4
1, 3 and 4
2, 3 and 4
State the volume of distilled water that is added to 5 cm3 of 6 % hydrogen peroxide to prepare 5% hydrogen peroxide solution.
0.08 cm3
0.8 cm3
8 cm3
80 cm3
Name the independent and dependent variables in this experiment
Independent variable: conc. of . actual rate of reaction
Dependent variable: rate of H2O2.
Independent variable: conc. of rate of reaction.
Dependent variable: rate of H2
Independent variable: conc. of time.
Dependent variable: rate of H2O
Independent variable: conc. of H2O2.
Dependent variable: rate of O2
Describe the shape of the graph
In these conditions, reaction rate is directly proportional to the enzyme concentration
The initial rate of the reaction increases linearly until the end of the reaction
At low concentrations, the graph will show an increasing rate of reaction as concentration increases, leveling off at higher concentrations
At low concentrations the graph will show an increase in reaction rate and at high enzyme concentrations it will show a plateau.
Identify ONE possible source of error during this experiment
Incorrect formulation of the hypothesis
Incorrect design of the experiment
Incorrectly identify the dependent and independent variables
Incorrect measurements of hydrogen peroxide and mashed potatoes; incorrect concentration of hydrogen peroxide
Which are properties of enzymes?
A
B
C
D
Which property of enzymes is explained by the lock and key hypothesis?
All enzymes are proteins
Enzymes are inactive at very low temperatures
Human enzymes are most active just below 40°C
Most enzymes can only catalyse one reaction
A student carried out experiments to investigate the effect of enzyme concentration on the rate of hydrolysis (break down) of protein in milk.
When the enzyme and milk were mixed, the protein was hydrolysed and the mixture changed from cloudy to clear.
The student investigated five different enzyme concentrations and recorded the time taken to reach the end-point for each.
What is an appropriate control for this investigation?
Carrying out a further experiment where the enzyme solution is replaced with water
Carrying out each experiment in a thermostatically regulated water-bath at 35 °C
Performing three repeat experiments for each of the five enzyme concentrations
Using the same volume of enzyme solution for each of the five experiments.
The enzyme invertase catalyses the breakdown of sucrose to glucose and fructose.
Three different enzyme inhibitors of invertase X, Y and Z were investigated. The percentage inhibition of invertase was measured at different concentrations of inhibitor.
The graph shows the result of the investigation.
Which are valid conclusions from these results?
1 The higher the concentration of inhibitor X, the less sucrose is broken down.
2 The production of glucose and fructose using inhibitor Y is higher than when inhibitor Z is used.
3 The production of glucose and fructose at an inhibitor concentration of 2 arbitrary units is lower than at an inhibitor concentration of 4 arbitrary units, for all inhibitors.
1 and 2
1 only
2 and 3
3 only
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
