9th – Biology – Chapter 7 – ENZYMES

MCQs

1. When an enzyme is exposed to a temperature far higher than its optimum, what occurs?
   a) It works faster indefinitely b) It becomes denatured and loses its structure c) It binds more substrates d) It changes its active site shape temporarily
2. Which of the following is an instance of a coenzyme?
   a) Iron ions b) Haem group c) Biotin d) NADP
3. Which cofactor serves as an example of a prosthetic group?
   a) NAD b) Magnesium ions c) Haem group d) Iron ions
4. Which of these is not a feature of enzymes?
   a) They speed up chemical reactions b) They are consumed in reactions c) They are highly specific d) They have an active site
5. Which of the following illustrates catabolism?
   a) Photosynthesis b) Protein synthesis c) Formation of glucose d) Lipolysis
6. What is the role of cofactors in the functioning of enzymes?
   a) Protein molecules that inhibit enzymes b) Non-protein molecules required for enzyme activity c) Substrates that bind to enzymes d) Enzymes that work in pathways
7. Which metabolic process requires an input of energy?
   a) Catabolism b) Anabolism c) Cellular respiration d) Oxidation
8. What may result when an enzyme is subjected to a temperature above its optimal level?
   a) Enzyme activity rate will increase b) Enzyme’s shape will change, potentially reducing its activity c) Enzyme will speed up the reaction and remain stable d) Enzyme will become a substrate itself
9. Which enzyme performs best in an acidic environment of pH 1.5 to 2.0?
   a) Trypsin b) Amylase c) Pepsin d) Lipase
10. Which statement about the specificity of enzymes is correct?
    a) Enzymes can catalyze any reaction b) Enzymes are highly specific to their substrates c) Enzymes only work with cofactors d) Enzymes are not proteins
11. What is the outcome when every active site of an enzyme is filled with substrate?
    a) The reaction rate increases indefinitely b) The enzyme denatures c) The reaction rate stabilizes due to saturation d) The enzyme binds inhibitors
12. Which enzyme is employed in the manufacture of cheese?
    a) Amylase b) Trypsin c) Pepsin d) Rennin
13. In what way does a competitive inhibitor interfere with enzyme action?
    a) Attaches to the substrate b) Changes enzyme shape c) Attaches and blocks the active site d) Blocks the cofactors
14. In which year was the Induced Fit Model put forward?
    a) 1894 b) 1958 c) 1920 d) 1975
15. How is the active site of an enzyme best described?
    a) The entire enzyme structure b) The region where substrates bind c) The part of the cell where enzymes are found d) The place where energy is stored
16. Which of the following serves as an example of a competitive inhibitor?
    a) Heavy metals b) Antibiotics c) NADP d) Enzymes
17. In which cell structure are ribozymes mainly located?
    a) Mitochondria b) Ribosomes c) Nucleus d) Cell membrane
18. Under which conditions do enzymes show their highest rate of activity?
    a) High substrate concentration b) Optimum temperature and pH c) Low pH only d) Denaturation
19. What effect does a non-competitive inhibitor have on an enzyme?
    a) It competes with the substrate for the active site b) It binds to the active site and blocks it c) It changes the enzyme’s shape by binding elsewhere d) It increases the enzyme’s activity
20. What function do coenzymes perform?
    a) Break down enzymes b) Bind loosely to enzymes and assist in reactions c) Inhibit enzyme function d) Form amino acids
21. What part do enzymes play in biochemical reactions?
    a) They slow down reactions b) They act as biological catalysts to speed up reactions c) They are consumed in the reaction d) They change the substrate into an inhibitor
22. At which pH does pepsin show its best activity?
    a) 7 b) 8 c) 1.5 – 2.0 d) 10
23. Which factor influences the activity of enzymes?
    a) Temperature b) pH c) Substrate concentration d) All of the above
24. Which scientist put forward the Lock and Key model?
    a) Daniel Koshland b) Emil Fischer c) Louis Pasteur d) Alexander Fleming
25. Which statement is correct as per the induced fit model of enzyme action?
    a) Enzyme’s active site changes shape to bind the substrate b) Substrate changes shape to bind to active site c) No shape changes occur in active site or substrate d) Substrate attaches the enzyme at a site other than active site
26. Which enzyme is responsible for catalyzing the breakdown of starch?
    a) Lipase b) Amylase c) Protease d) Trypsin
27. The Lock and Key Model of enzyme action was suggested by whom?
    a) Daniel Koshland b) Louis Pasteur c) James Watson d) Emil Fischer
28. An enzyme has its best activity at pH 7.4 and is then placed in an acidic solution of pH 4.0. What will be the effect on the enzyme?
    a) The active site will be modified, reducing substrate binding b) The enzyme will catalyse reactions faster due to increased H ions c) The enzyme will gain additional active sites d) The substrate will become inactive in an acidic environment
29. Which of these is an example of a non-competitive inhibitor?
    a) Antibiotics b) Biotin c) Mercury d) NAD
30. Which statement correctly describes the optimum pH of the digestive enzymes pepsin and trypsin?
    a) Pepsin works at low pH while trypsin works at high pH b) Both work at high pH c) Both work at low pH d) Pepsin works at high pH while trypsin works at low pH
31. What is the chemical nature of enzymes?
    a) Lipids b) Carbohydrates c) Proteins d) Nucleic acids
32. According to the Lock and Key Model, how does the substrate relate to the enzyme?
    a) The active site reshapes to fit the substrate b) The substrate fits precisely into a fixed active site c) The substrate binds to a cofactor d) The enzyme changes its overall shape
33. As per the Induced Fit Model, what happens to the active site?
    a) It remains rigid throughout the reaction b) It is reshaped when the substrate binds c) It binds to inhibitors only d) It releases the substrate unchanged
34. Which description fits prosthetic groups?
    a) Required by all enzymes b) Proteins in nature c) Loosely attached to enzymes d) Tightly bound to enzymes
35. How do inhibitors act on the enzyme in competitive inhibition?
    a) They bind to a site other than the active site b) They compete with the substrate for the active site c) They permanently denature the enzyme d) They increase the reaction rate
36. In what way are enzymes useful in the paper industry?
    a) They break down proteins b) They degrade starch to lower viscosity c) They remove stains d) They produce alcohol
37. Which statement defines an enzyme most accurately?
    a) A chemical that breaks down food b) A hormone that regulates metabolism c) A protein that speeds up reactions d) A molecule that stores energy
38. Which of the following is a cofactor of inorganic nature?
    a) Biotin b) NAD c) Magnesium ions d) Haem group
39. What is the pocket on an enzyme, in which catalysis takes place, called?
    a) Substrate site b) Active site c) Cofactor site d) Inhibitor site
40. How does the reaction rate respond when substrate concentration is raised?
    a) Reaction rate always increases b) Reaction rate remains unchanged c) Reaction rate increases until enzyme saturation d) Reaction rate decreases
41. Which industry makes use of enzymes to degrade starch in paper manufacturing?
    a) Fermentation industry b) Food industry c) Paper industry d) Dairy industry
42. For most human enzymes, which temperature is optimum?
    a) 25°C b) 37°C c) 45°C d) 60°C
43. How is enzyme activity affected when the pH changes considerably?
    a) It increases indefinitely b) It slows down or stops due to ionization changes c) It becomes more specific d) It binds more cofactors
44. In which industry are enzymes applied to break down starch and proteins for fermentation?
    a) Food industry b) Fermentation industry c) Paper industry d) Detergent industry
45. Which kind of enzymes function inside cells?
    a) Extracellular enzymes b) Intracellular enzymes c) Prosthetic enzymes d) Competitive enzymes
46. Which organic cofactor is bound tightly to enzymes?
    a) Coenzymes b) Prosthetic groups c) Nucleotides d) Metal ions
47. Enzymes are used for cheese production in which industry?
    a) Paper industry b) Food industry c) Biological detergent d) Fermentation industry
48. Which of the following enzymes is released outside the cell?
    a) Trypsin b) Amylase c) Catalase d) RNA polymerase
49. What do cofactors do for enzymes?
    a) Increase reaction time b) Enhance enzyme activity c) Inhibit enzyme function d) Provide energy
50. Why do enzymes show specificity in their action?
    a) Their active sites fit specific substrates b) They are always proteins c) They are consumed in reactions d) They work only at high temperatures
51. Which temperature is the optimum for the majority of human enzymes?
    a) 50°C b) 37°C c) 10°C d) 60°C
52. What is the consequence for enzymes placed at temperatures above their optimum?
    a) They become more active b) They get denatured c) They form new enzymes d) They stop reacting completely
53. How is metabolism defined in living organisms?
    a) The breakdown of complex molecules into simpler ones b) The sum of all chemical reactions to sustain life c) The building of complex molecules from simpler ones d) The production of enzymes in cells
54. Trypsin functions in the small intestine. What is its optimum pH?
    a) 1.5 b) 5 c) 10 d) 7.8
55. Of what are enzymes chiefly composed?
    a) Carbohydrates b) Lipids c) Proteins d) Nucleic acids
56. What is the effect of a rise in temperature on enzyme activity?
    a) Increases activity to a point b) Always decreases activity c) Makes enzymes non-functional d) No effect on enzyme
57. Which enzyme carries out its function within the cell?
    a) Extracellular enzyme b) Intracellular enzyme c) Coenzyme d) Lipase
58. Which of the following is a feature of enzymes?
    a) They are non-specific to substrates b) They have a globular structure c) They are mostly carbohydrates d) They function only outside cells
59. In fermentation, which substances do enzymes break down to help yeast?
    a) Lipids and glycerol b) Starch and proteins into sugars and amino acids c) Nucleic acids d) Heavy metals
60. Which enzyme specifically converts starch into simple sugars?
    a) Pepsin b) Trypsin c) Lipase d) Amylase
61. Which process joins small molecules together to make larger ones?
    a) Catabolism b) Anabolism c) Denaturation d) Inhibition
62. Which enzyme is added to biological detergents to remove protein stains?
    a) Amylase b) Protease c) Lipase d) Cellulase
63. How would you define metabolism?
    a) The breakdown of molecules only b) The sum of all chemical reactions in an organism c) The formation of complex molecules only d) The process of digestion
64. Which type of enzyme in biological detergents helps remove protein stains?
    a) Amylase b) Protease c) Lipase d) Trypsin
65. What is meant by the phrase “saturation of active sites”?
    a) All active sites are occupied by substrates b) The enzyme is denatured c) Inhibitors block all active sites d) The enzyme works at a slower rate
66. How is a non-competitive inhibitor best described?
    a) A molecule that binds to the active site b) A molecule that binds to another site and changes enzyme shape c) A molecule that increases enzyme activity d) A molecule that forms an enzyme-substrate complex
67. What results when the pH of an enzyme’s surroundings changes drastically?
    a) Enzyme activity increases b) The enzyme stops working c) The enzyme produces more substrate d) The enzyme becomes smaller
68. Which products are formed in cellular respiration?
    a) Oxygen and water b) Carbon dioxide and energy c) Proteins d) Starch
69. What role do ribozymes perform?
    a) Breaking down proteins b) Acting as biological catalysts c) Transporting molecules d) Providing structural support
70. As per the induced fit model, what takes place when a substrate attaches to an enzyme?
    a) The enzyme’s shape remains unchanged b) The enzyme is permanently altered c) The active site changes shape to fit the substrate d) The substrate changes its structure
71. Which of the following is an example of an extracellular enzyme?
    a) Enzymes of cellular respiration b) Enzymes secreted into the stomach cavity c) Enzymes in the mitochondria d) Enzymes in the nucleus
72. Which kind of RNA molecule is capable of acting as an enzyme?
    a) Ribozyme b) Messenger RNA c) Transfer RNA d) Micro RNA
73. What are substances that lower enzyme activity called?
    a) Substrates b) Cofactors c) Inhibitors d) Coenzymes
74. Which model proposes that the active site has a fixed structure?
    a) Induced Fit Model b) Competitive Inhibition Model c) Non-Competitive Inhibition Model d) Lock and Key Model
75. What is the action of enzyme inhibitors?
    a) Increase enzyme activity b) Block or slow down enzyme activity c) Help enzymes bind to substrates d) Provide energy to enzymes
76. Which animal is known to possess one of the highest metabolic rates?
    a) Elephants b) Hummingbirds c) Pythons d) Sharks
77. Which of the following exemplifies catabolism?
    a) Photosynthesis converting CO₂ and water into glucose b) Protein synthesis forming proteins from amino acids c) Cellular respiration oxidizing glucose into CO₂ and H₂O d) Formation of lipids from fatty acids
78. What is the main aim of anabolism?
    a) To release energy by breaking down molecules b) To build complex molecules from simpler ones using energy c) To speed up chemical reactions d) To inhibit enzyme activity
79. Which of the following is an inorganic cofactor?
    a) NADP b) Magnesium ions c) Biotin d) Coenzyme A
80. How is a competitive inhibitor defined?
    a) A molecule that attaches to the active site and competes with the substrate b) A molecule that binds elsewhere on the enzyme c) A molecule that speeds up the reaction d) A molecule that breaks down enzymes
81. Which of these is an example of a competitive inhibitor?
    a) Heavy metals b) Antibiotics c) Cancer therapy drugs d) Mercury
82. Which process splits lipids into fatty acids and glycerol?
    a) Lipolysis b) Photosynthesis c) Protein synthesis d) Denaturation
83. What are all enzymes basically made of?
    a) Nucleic acids b) Proteins c) Carbohydrates d) Lipids

Short Questions

1. Define metabolism. Differentiate between catabolism and anabolism.
2. How does a non-competitive inhibitor affect enzyme activity?
3. Differentiate between competitive and non-competitive inhibition.
4. What is meant by optimum temperature for enzymes?
5. Which enzyme is used in dishwashing detergents?
6. What are cofactors?
7. Where are ribozymes found?
8. How does enzyme saturation limit the reaction rate?
9. Define non-competitive inhibition.
10. Why do most human enzymes work best at 37°C?
11. How do competitive inhibitors work?
12. Define competitive inhibition.
13. Why is the induced fit model considered more accurate?
14. How does the induced fit model differ from the lock and key model?
15. What are the two types of metabolism?
16. Define intracellular and extracellular enzymes with examples.
17. Why is the induced fit model preferred over the lock-and-key model?
18. What is meant by the specificity of enzymes?
19. What happens to enzymes when pH levels change drastically?
20. Define catabolism with an example.
21. Give an example of a non-competitive inhibitor.
22. How are enzymes used in the food industry?
23. What is the structure of enzymes?
24. Why do competitive inhibitors affect enzyme activity more than non-competitive inhibitors?
25. Why are enzymes not consumed in a reaction?
26. Who proposed the induced fit model and when?
27. How are enzymes helpful in the paper industry?
28. Which type of metabolism demands input of energy? Give an example.
29. Give an example of a competitive inhibitor.
30. Which type of enzyme inhibitors inhibit the enzymes without attaching to the active site?
31. How are enzymes used in the fermentation industry?
32. What is enzyme denaturation?
33. How do enzymes function in metabolic pathways?
34. What is meant by enzyme saturation?
35. Provide two examples of enzymes that operate optimally at specific pH.
36. What is an active site of an enzyme?
37. How does substrate concentration affect enzyme activity?
38. Explain the lock-and-key model in simple terms.
39. How do enzymes work in biological detergents?
40. What is metabolism?
41. How does pH affect enzyme activity?
42. What is the chemical nature of enzymes?
43. What is the optimum pH of pepsin and trypsin?
44. Why are enzymes important in different industries?
45. What do you mean by optimum temperature and pH?
46. What would happen if there were no enzymes in living organisms?
47. Who proposed the lock-and-key model?
48. Name an enzyme used in bread production.
49. How do enzymes speed up biochemical reactions?
50. Give an example of an inorganic cofactor.
51. Why are enzymes called biological catalysts?
52. How does metabolism sustain life?
53. Why do hummingbirds have high metabolic rates?
54. How can temperature both increase and decrease enzyme activity?
55. Define an enzyme. What is its role in metabolism?
56. What is the difference between prosthetic groups and coenzymes?
57. What happens to enzymes when the temperature exceeds their optimum level?
58. How do antibiotics act as enzyme inhibitors?
59. What is an enzyme inhibitor?
60. What is the active site of an enzyme? State its importance in enzyme specificity.
61. What are the two main types of cofactors?
62. Give an example of a coenzyme.
63. Why do different enzymes have different optimum pH values?
64. What is a ribozyme?
65. What are enzymes?
66. How does pH affect enzyme activity?
67. Why is an enzyme’s shape important for its function?
68. Define anabolism with an example.
69. How do enzymes recognize their specific substrates?
70. Provide an example of a specific enzyme-substrate pair.

Long Questions

1. What is enzyme inhibition? Explain competitive and non-competitive inhibition with examples.
2. Describe the factors affecting enzyme activity with graphical representation.
3. Describe the characteristics of enzymes.
4. What is the role of enzymes in metabolic pathways? Explain with an example.
5. Explain the mechanism of enzyme action with the help of models.
6. Describe how temperature extremes can inhibit enzyme activity and lead to enzyme denaturation.
7. Compare and contrast the lock-and-key model with the induced fit model.
8. How does pH affect enzyme activity?
9. Discuss the industrial applications of enzymes in different fields.
10. Compare the Lock-and-Key and Induced Fit models of enzyme action.
11. Briefly describe the factors that affect the activity of enzymes.
12. Define metabolism. Explain its types with examples.
13. What are enzymes? Describe their characteristics in detail.
14. What are cofactors? Explain their types with examples.
15. Differentiate between intracellular and extracellular enzymes with examples.

Answer Key

1. b) It becomes denatured and loses its structure
2. d) NADP
3. c) Haem group
4. b) They are consumed in reactions
5. d) Lipolysis
6. b) Non-protein molecules required for enzyme activity
7. b) Anabolism
8. b) Enzyme’s shape will change, potentially reducing its activity
9. c) Pepsin
10. b) Enzymes are highly specific to their substrates
11. c) The reaction rate stabilizes due to saturation
12. d) Rennin
13. c) Attaches and blocks the active site
14. b) 1958
15. b) The region where substrates bind
16. b) Antibiotics
17. b) Ribosomes
18. b) Optimum temperature and pH
19. c) It changes the enzyme’s shape by binding elsewhere
20. b) Bind loosely to enzymes and assist in reactions
21. b) They act as biological catalysts to speed up reactions
22. c) 1.5 – 2.0
23. d) All of the above
24. b) Emil Fischer
25. a) Enzyme’s active site changes shape to bind the substrate
26. b) Amylase
27. d) Emil Fischer
28. a) The active site will be modified, reducing substrate binding
29. c) Mercury
30. a) Pepsin works at low pH while trypsin works at high pH
31. c) Proteins
32. b) The substrate fits precisely into a fixed active site
33. b) It is reshaped when the substrate binds
34. d) Tightly bound to enzyme
35. b) They compete with the substrate for the active site
36. b) They degrade starch to lower viscosity
37. c) A protein that speeds up reactions
38. c) Magnesium ions
39. b) Active site
40. c) Reaction rate increases until enzyme saturation
41. c) Paper industry
42. b) 37°C
43. b) It slows down or stops due to ionization changes
44. b) Fermentation industry
45. b) Intracellular enzymes
46. b) Prosthetic groups
47. b) Food industry
48. b) Amylase
49. b) Enhance enzyme activity
50. a) Their active sites fit specific substrates
51. b) 37°C
52. b) They get denatured
53. b) The sum of all chemical reactions to sustain life
54. d) 7.8
55. c) Proteins
56. a) Increases activity to a point
57. b) Intracellular enzyme
58. b) They have a globular structure
59. b) Starch and proteins into sugars and amino acids
60. d) Amylase
61. b) Anabolism
62. b) Protease
63. b) The sum of all chemical reactions in an organism
64. b) Protease
65. a) All active sites are occupied by substrates
66. b) A molecule that binds to another site and changes enzyme shape
67. b) The enzyme stops working
68. b) Carbon dioxide and energy
69. b) Acting as biological catalysts
70. c) The active site changes shape to fit the substrate
71. b) Enzymes secreted into the stomach cavity
72. a) Ribozyme
73. c) Inhibitors
74. d) Lock and Key Model
75. b) Block or slow down enzyme activity
76. b) Hummingbirds
77. c) Cellular respiration oxidizing glucose into CO₂ and H₂O
78. b) To build complex molecules from simpler ones using energy
79. b) Magnesium ions
80. a) A molecule that attaches to the active site and competes with the substrate
81. b) Antibiotics
82. a) Lipolysis
83. b) Proteins