Download Enzyme Quiz - BiologySemester57

Name: ________________________________
Knowledge:
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Enzyme Quiz
Multiple Choice (9 marks)
____ 1.
a.
b.
c.
d.
e.
Of the following characteristics, which one is not true about enzymes?
They are essential to the metabolism of cells for the conversion of energy.
They function best at specific temperatures but break down at high temperatures.
Some enzymes need activators or cofactors.
They function best at a particular pH.
They undergo major chemical change after reacting with their specific substrate.
____ 2.
a.
b.
c.
d.
e.
Of the following five statements, which is most correct with respect to enzymes?
A denatured enzyme is more specific in its action.
Denaturation of proteins always involves enzymes.
Catalysts prevent chemical reactions.
All catalysts are enzymes.
All enzymes are catalysts.
____
3. At which temperature would you expect any enzyme extracted from a human tissue to have its
optimal performance?
a. 5°C
d. 37°C
b. 10°C
e. 95°C
c. 25°C
____
4. At high temperatures, the rate of enzyme action decreases because the increased heat
a. changes the pH of the system
b. alters the active site of the enzyme
c. neutralizes the acids and bases in the system
d. increases the concentration of the enzyme
____
5. Enzymes work as catalysts by doing which of the following?
a. increasing the free energy of the reactants
b. decreasing the free energy of the reactants
c. increasing the activation energy
d. decreasing the activation energy
e. bypassing the need for a transition state to occur
____
6. Which of the following statements regarding enzyme inhibition is incorrect?
a. Competitive inhibitors have a similar structure to the normal substrate.
b. Competitive inhibitors bind to the active site of an enzyme.
c. Noncompetitive inhibition can be overcome by adding more substrate.
d. Noncompetitive inhibitors do not have a similar structure to the normal substrate.
e. Noncompetitive inhibitors do not bind to the active site of an enzyme.
____
7. The "lock and key hypothesis" attempts to explain the mechanism of
a. vacuole formation
b. pinocytosis
c. sharing of electrons
d. enzyme specificity
____
8. At
a.
b.
c.
d.
____
9. Which environmental condition would most likely have the least effect on the rate of enzyme
controlled hydrolytic reactions in humans?
a. the pH of the solution
b. the temperature of the solution
c. the amount of enzyme present
d. the amount of light present
about 0°C, most enzymes are
inactive
active
destroyed
replicated
Short Answer Questions (11marks)
Answer each of the following questions in the space provided.
10. Using your knowledge of enzyme structure and function, explain why a prolonged period of
high fever is dangerous to humans. (2)
11. Draw a graph showing the effect of increasing substrate concentration on the rate of
enzyme activity. (1)
12.
Examine the following data that are related to a variety of enzymes, which have been
tested at a number of temperatures and pH levels to measure their activities.
Enzyme Activity (mmol/ug of enzyme protein/min) for Enzyme 'A'
T=4°C
T=20°C
T=37°C
T=45°C
T=80°C
pH=1
0
0
0
0
0
pH=4
0
2
10
2
0
pH=7
0
5
50
5
0
pH=10
0
2
10
2
0
pH=13
0
0
0
0
0
Enzyme Activity (mmol/ug of enzyme protein/min) for Enzyme 'B'
T=4°C
T=20°C
T=37°C
T=45°C
T=80°C
pH=1
0
2
10
2
0
pH=4
0
2
10
2
0
pH=7
0
2
10
2
0
pH=10
0
2
10
2
0
pH=13
0
2
10
2
0
Enzyme Activity (mmol/ug of enzyme protein/min) for Enzyme 'C'
T=4°C
T=20°C
T=37°C
T=45°C
T=80°C
pH=1
0
0
0
0
0
pH=4
2
2
2
2
2
pH=7
10
10
10
10
10
pH=10
2
2
2
2
2
pH=13
0
0
0
0
0
Complete the following table based on these results. (3)
Enzyme
A
B
C
Optimal Temperature
Optimal pH
13. a) Add descriptions to this diagram to explain how the enzyme sucrase catalyzes the breakdown
of sucrose into glucose and fructose (2.5).
b) This particular reaction is used to make products that we can find at a supermarket or a
department store. Name one product that relies on this reaction. (0.5)
14. Alcohols compose a very large family of organic molecules. The alcohol found in beer, wine
and distilled spirits is ethanol. The breakdown of ethanol in humans begins with an enzyme called
alcohol dehydrogenase, which is found in the liver. Accidental ingestion of methanol, an alcohol
that is poisonous, can be treated by giving the person ethanol. This method works by enzyme
inhibition. By looking at the chemical structures below, is ethanol a competitive or
noncompetitive inhibitor of methanol? Explain. (2)