BIOLOGY PRACTICE QUESTIONS FOR GRADE 11 STUDENTS FROM UNIT THREE

Instruction I: Say True For Correct Statement And False For Incorrect Statement.

1. Enzymes are consumed in the reactions they catalyze.

2. Enzymes work best at a specific pH and temperature.
3. Enzymes speed up reactions by lowering the activation energy required.
4. Enzymes can catalyze any type of reaction.
5. All enzymes are proteins.
6. A competitive inhibitor binds to the enzyme’s active site and prevents the substrate from
binding.
7. Non-competitive inhibitors bind to the active site of an enzyme.
8. Enzymes can function outside of their optimum pH and temperature range, but their
efficiency decreases.
9. Coenzymes are inorganic molecules that assist in enzyme function.
10. Enzymes only function in the presence of water.
11. Enzymes are biocatalyst proteins.
12. The rate of enzymatic reaction increases with increased rate of substrate concentration.
13. Inhibitor is a molecule that reduces the rate of enzyme-catalyzed reactions.
14. If you drop H2O2 on slice of boiled potato, enzymatic reactions are very active.
15. The suffix “ase” indicates that a molecule is an enzyme.
16. All enzymes are protein molecules, but not all proteins are enzymes.
17. Our saliva contains an enzyme amylase.
18. Enzymes can react beyond the optimum pH.
19. Activators are molecules that increase the activity of enzymes.
20. Enzymes are drugs in the pharmaceutical industry.
21. Hemogelobin has tertiary structure.
22. DNA polymerase has quaternary structure.
23. Amino acid sequence determines shape and function of enzymes.
24. Uncompetitive inhibition and competitive inhibition reduces enzyme action in the same way.
25. Enzymes divide based on there function.
Instruction II: Choose the Best Answer From The Given Alternative
1. What is the optimum temperature of enzyme activity in human body?
A. 25 - 30 ºC C. 40 - 55 ºC
B. 35 - 45 D. 37 ºC 2.
2. What is the first discovered enzyme?
A. Lactase C. Ligases
B. Diastase D. Hydrolase
3. An enzyme acts best at a particular pH called
A. Catalytic pH C. Abnormal pH
B. Optimum pH D. All

4. The two enzyme specificity models are

A. Lock and Key C. Induced fit model
B. Active site and allosteric site D. A and B
5. Which of the following statement is incorrect?
A. Enzymes are protein in nature C. Enzymes is colloidal in nature
B. Enzymes are thermo-labile D. Enzymes are inorganic catalyst
6. What is enzyme kinetics?
A. The rate of reaction C. Basic reactions
B. Acidic reactions D. Heat reaction
7. What is the molecular weight of enzymes?
A. Large protein biomolecules C. 200 to 300 peptide bonds
B. 2001 to 3001 amino acids D. all
8. Enzymes that have additional binding sites
A. Allosteric enzymes C. Enzyme rates
B. Transition state D. None
9. Enzyme activity is dependent on
A. The folding of a proteins C. Sensitivity to the temperature
B. Salt concentration D. All
10. What is the formula for the rate enzyme kinetic mechanism?
A. S ⇄ ES ⇄ ES* ⇄ EP ⇄ E + P C. S + ES ⇄ ES* ⇄ EP ⇄ E + P
B. S ⇄ ES ⇄ ES ⇄ EP ⇄ E + P D. S ⇄ ES ⇄ ES* ⇄ EP ⇄ P
11. The three steps of malting are
A. Germinating, Steeping and Kilning C. Kilning, Germinating and Steeping
B. Steeping, Germinating and Kilning D. None of the steps is correct
12. An enzyme that carries and transfers methyl groups from one compound donor (Cofactor)
to another compound (acceptor) is
A. Transferase C. Lyases
B. Isomerases D. Translocases
13. Which of the following is an example of a protein-digesting enzyme?
A. Amylase C. Trypsin
B. Lipase D. Lactase
14. The enzyme that breaks down hydrogen peroxide into water and oxygen is called:
A. Catalase C. Lipase
B. Amylase D. Pepsin
15. Which of the following statements about enzymes is true?
A) Enzymes are consumed during the reaction.
B) Enzymes increase the activation energy required for reactions.
C) Enzymes are highly specific for their substrates.
D) Enzymes only function in the presence of high heat.
Answer: C) Enzymes are highly specific for their substrates.
16. The shape of an enzyme's active site is primarily determined by:
A. The enzyme's substrate concentration
B. The temperature of the reaction
C. The amino acid sequence of the enzyme
D. The pH of the environment
17. Which type of enzyme inhibition occurs when a molecule binds to the enzyme's active
site, preventing the substrate from binding?
A. Allosteric inhibition C. Non-competitive inhibition
B. Competitive inhibition D. Uncompetitive inhibition
18. Which of the following enzymes is used to digest fats?
A. Trypsin C. Lipase
B. Amylase D. Pepsin
 19. Enzymes are typically classified based on:
A. Their molecular weight C. Their color
B. Their function D. Their structure
20. What is the role of coenzymes in enzyme activity?
A. They increase the pH of the enzyme’s environment
B. They act as permanent inhibitors of enzymes
C. They help the enzyme to catalyze reactions by accepting or donating electrons
D. They denature the enzyme after a reaction
21. What is the effect of increasing the temperature on enzyme activity?
A. It always increases the rate of the reaction.
B. It has no effect on enzyme activity.
C. It can increase the rate of reaction up to a point, but then it can denature the enzyme
D. It decreases the reaction rate by reducing enzyme stability/
22. What is an enzyme's "active site"?
A. The part of the enzyme that binds with water molecule
B. The part of the enzyme that binds to its substrate and facilitates the reaction
C. The part of the enzyme that is involved in protein synthesis
D. The region where the enzyme is synthesized
23. The term "enzyme specificity" refers to:
A. The enzyme's ability to function in extreme condition
B. The enzyme's ability to catalyze multiple different reactions
C. The enzyme's ability to act only on a particular substrate or class of substrates
D. The enzyme's preference for non-polar substrates
24. Suppose enzyme ‘A’ digests proteins in the stomach at pH =2 and Enzyme ‘B’ digests
proteins in the small intestine at pH = 8. Which of the following is NOT true?
A. Enzyme ‘A’ would be denatured in the small intestine.
B. Enzyme ‘A’ works best in acidic conditions.
C. Enzyme ‘A’ can also work in the small intestine.
D. Enzyme ‘A’ helps in the hydrolysis of proteins.
25. The graph below shows the effect of substrate concentration on the action of enzyme Y.
This enzyme is functioning at its optimal temperature 36°C and at its optimal PH 5.5.

When the substrate concentration increases from 0.4% to 0.5%, the rate of the reaction:
A. Decreases C. Increases
B. Remains constant D. Gradually decrease
26. At which level of structural organization do proteins have the alpha helix shape?
A. Primary structure C. Tertiary structure
B. Secondary structure D. Quaternary structure
27. The process of breaking the intra and inter molecular non-covalent bond of enzyme is
A. Solubility C. Biocatalyst
B. Denaturation D. Reversibility
28. Which of the following factor does not denature the enzyme structure in human body?
A. Temperature of 37 OC C. Heavy metals
B. Alterations in PH D. B and C
29. Which of the following is the region where a substrate binds on an enzyme?
A. Allosteric site C. Substrate site
B. Active site D. Binding area
30. Which model describes the specificity of enzymes for their substrate?
A. Competitive binding model C. Lock and key model
B. Substrate binding model D. Induced fit model
31. What happens to an enzyme after the reaction is complete? It is
A. Reused C. Permanently used up
B. destroyed D. Combines with products
32. What type of inhibition occurs when the inhibitor binds to the enzyme out of active site?
A. Irreversible C. Non-competitive
B. Competitive D. Uncompetitive
33. Which of the following is true about enzyme substrate model? According to
A. Lock and key model, enzyme act as key and substrate act as lock.
B. Induced fit model, enzyme inhibition is property of enzyme.
C. Induced fit model, substrate act as key and enzyme act as lock.
D. Induced fit model, active site and substrates are naturally complementary.
34. Which statement best describes the enzyme represented in the graphs?

A. This enzyme works best at a temperature above 50°C and a pH above 12

B. This enzyme works best at a temperature of 35°C and a pH of 8.
C. This enzyme works best at a temperature of 50°C and a pH of 12.
D. Temperature and pH have no effect on the action of this enzyme.
35. The graph shows the relative rates of action of four enzymes, A, B, C, and D. Which
enzyme shows the greatest change in its rate of action with the least change in pH?

A. Enzyme A C. Enzyme C
B. Enzyme B D. Enzyme D
36. In the above graph on question 11. Which two enzymes would function in a region of the
human body having a neutral pH?
A. Enzymes A and B C. Enzymes C and D
B. Enzymes B and C D. Enzymes B and D

37.A molecule of an enzyme that has a high turnover number:

A. Can easily be denatured
B. Can easily be replaced with another enzyme
C. Converts substrate to product very rapidly
D. Needs a constant supply of cofactors
38. The optimum temperature of an enzyme is the temperature at which:
A. There is no denaturation
B. The maximum number of enzyme–substrate complexes are formed
C. There is the maximum number of collisions between enzyme and substrate
D. the particles have the most kinetic energy
39. The protein portion of a conjugated enzyme is called a(n)
A. Apo enzyme. C. Holoenzyme.
B. Coenzyme. D. cofactor
40. Which of the following enzyme properties is explained by the lock-and-key model for
enzyme action?
A. high turnover rate C. absolute specificity
B. susceptibility to denaturation D. susceptibility to deactivation
41. An enzyme active site is the location in the enzyme where:
A. Protein side groups are brought together by bending and folding to form a site for
interactions with substrates
B. The catalyst interactions with the enzyme
C. Catalyst molecules are generated
D. The substrate creates the catalyst molecules
42. The number of substrate molecules acted upon per minute by one molecule of enzyme is
called the:
A. Active site number C. Enzyme activity number
B. turnover number D. Optimum number.
43. Which of the following statements concerning a competitive enzyme inhibitor is correct?
A. it competes with substrate for occupancy of the enzyme's active site
B. binds at the active site simultaneously with the substrate
C. it breaks the enzyme down to its constituent amino acids
D. its effect can be overcome by increasing the temperature
44. Which of the following binds to an enzyme at a location other than the active site?
A. Substrate C. Irreversible inhibitor
B. reversible competitive inhibitor D. reversible noncompetitive inhibitor

Instruction III: Give Sort Answer For The Following Questions

1. What are intrinsic and extrinsic enzymes? Give examples for each.
2. What type of inhibition occurs when inhibitor binds to enzyme out of active site?
3. Identify competitive, non-competitive and uncompetitive inhibitions.
4. What happen on activation energy during enzyme activity?
5. What happens to an enzyme after the reaction is completed?
6. What is the function of enzyme in disease treatment?
7. At which level of structural organization do proteins have beta sheet structure?
8. Describe properties of enzymes such as solubility, denaturation and biocatalyst.
9. To which biological molecules do enzymes belong?
10. What is the difference between Induced fit model and Lock and key model?
11. Identify allosteric site and Active site.
12. Enlist factors affecting enzyme activity.

Set by: Fikadu K