Biology For Class IX - Chapter No.6 - ENZYMES - MCQs and Fill In the Blanks

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CHAPTER 6: ENZYMES
Multiple Choice Questions (MCQs)

By Mrs. Ayesha Arif
(Jauhar Progressive School

1. Encircle the correct answer:
(i) All are characters of enzymes except:
(a) Enzyme speed up a biochemical reaction.
(b) Enzymes are sensitive to minor change in pH
(c) Enzyme activity enhanced by inhibitors ✔
(d) Enzyme portion where substrate attach called active site

(ii) Enzymes are:
(a) Steroid in nature
(b) Protein in nature ✔
(c) Lipid in nature
(d) Carbohydrate in nature

(iii) Metabolic reactions are:
(I) Constructive reactions
(II) Destructive reactions
(III) Inhibiting reactions
(a) I only
(b) I and II only ✔
(c) I, II and III
(d) II and III only

(iv) The point where the enzyme is most active is known as:
(a) Neutral pH
(b) Acidic pH
(c) Basic pH
(d) Optimum pH ✔

(v) Active site continuously changes it shapes until the substrate do not bind to it, is statement of:
(a) Induce fit model ✔
(b) Lock and key model
(c) Fluid mosaic model
(d) Both “a” and “b”

(vi) Select the mismatched:
(a) Proteases → Carbohydrate
(b) Lipases → Lipids
(c) Trypsin → Protein
(d) All are correctly matched ✔

(vii) Chemical reaction requires particular conditions to carry down at proper rate, especially:
(a) Temperature and Nature
(b) Nature and Pressure
(c) Nature and Structure
(d) Temperature and Pressure ✔

(viii) All are factors affecting enzyme activity except:
(a) pH
(b) Substrate concentration
(c) Organic solvent ✔
(d) Temperature

(ix) Rate of reaction will increase when temperature:
(a) Increases ✔
(b) Decreases
(c) Below 10°C
(d) Both “a” and “c”

(x) Choose the correct statement regarding lock and key model.
(a) Enzyme and substrate posses' specific complementary geometric shapes. ✔
(b) Active site of enzyme is flexible
(c) Active site continuously changes
(d) All above statements are correct.

11. Reactions of an organism are collectively called:
a) Metabolic reactions ✔
b) Anabolic reactions
c) Catabolic reactions
d) complex reactions

12. The phenomenon of chemical activity in an organism is called:
a) disjunction
b) Terminalization
c) Anabolism
d) Metabolism ✔

13. The metabolic activities are always of:
a) Two types ✔
b) Three types
c) Four types
d) Five types

14. In constructive reactions, large molecules are formed to form a structure of cell or body. These reaction ere called:
a) Metabolic reactions
b) Anabolic reactions ✔
c) Catabolic reactions
d) complex reaction

15. In destructive reactions, large molecules breakdown in small molecules to produce energy is called:
a) metabolic reactions
b) anabolic reactions
c) catabolic reactions ✔
d) complex reaction

16. The minimum amount of energy, a reaction requires to initiate, is called:
a) metabolic energy
b) anabolic energy
c) catabolic energy
d) activation energy ✔

17. The bio-catalysts which facilitate chemical reaction by lowering activation energy is called:
a) enzymes ✔
b) hormones
c) inhibitors
d) substrate

18. Its action allows biological reaction to proceed rapidly at relatively low temperature and pressure tolerable by living organism:
a) substrate
b) hormones
c) enzymes ✔
d) inhibitor

19. Enzymes are bio-catalyst made up of mostly:
a) chitin
b) carbohydrates
c) lipid
d) protein ✔

20. Enzymes have specific shape with three dimensionally folded chains of:
a) ether
b) amino acid ✔
c) amide
d) ester

21. Reactants of enzyme are called:
a) substrate ✔
b) inhibitor
c) hormones
d) yeast

22. A small portion of enzyme where substrate attaches with enzyme is called:
a) substrate
b) inhibitor
c) hormones
d) active site ✔

23. Enzymes are sensitive to a minor change in:
a) pH, pressure and density
b) PH, temperature and pressure
c) pH, substrate concentration and pressure
d) pH, temperature and substrate concentration ✔

24. Activity of enzymes can be enhanced by:
a) inhibitors
b) cofactor
c) activator ✔
d) hormones

25. By inhibitor, the activity of enzymes can be:
a) increased
b) decreased ✔
c) remained the same
d) first increased & then decreased

26. If the amount of the enzyme is kept constant and the substrate concentration is then gradually increased, the reaction velocity will:
(a) decrease
(b) increase
(c) decrease until it reaches a maximum
(d) increase until it reaches a maximum ✔

27. The protein nature of the enzymes makes them extremely sensitive to:
(a) thermal changes ✔
(b) pressure changes
(c) density changes
(d) substrate changes

28. Enzymes activity occurs within a:
(a) narrow range of pressures
(b) wide range of pressures
(c) narrow range of temperatures ✔
(d) wide range of temperatures

29. The protein nature of the enzymes makes them sensitive to:
(a) pressure changes
(b) pH ✔
(c) density changes
(d) Kinetic energy

30. All enzymes work at their maximum rate at:
(a) wide range of pressure
(b) narrow range of pressure
(c) wide range of pH
(d) narrow range of pH ✔

31. The point where the enzyme is most active is known as:
(a) active pH
(b) maximum pH
(c) optimum pH ✔
(d) cutoff pH

32. It works at a low pH i.e., it is highly acidic.
(a) Pepsin✔
(b) Trypsin
(c) proteases
(a) lipase

33. It works at a high pH is:
(2) Pepsin
(b) Trypsin ✔
(c) proteases
(d) lipase

34. Most enzymes work at neutral pH:
(a) 6.2
(b) 6.4
(c) 7.2
(d) 7.4 ✔

35. In 1894, the lock and key model theory was first postulated by:
(a2) Zachanan Janson
(b) Walter Fleming
(c) Emil Fischer ✔
(d) Daniel Koshland

36. In 1958, the induced fit model suggested by:
(a) Zachanan Janson
(b) Walter Fleming
(c) Emil Fischer
(d) Daniel Koshland ✔

37. In the human body, the number of known enzymes is more than:
(a) 1000 ✔
(b) 700
(c) 500
(d) 100

38. These are the enzymes which catalyzes the proteins.
(a) Lipase
(b) Proteases ✔
(c) Pepsin
(d) Trypsin

39. This enzyme acts on lipids only.
(a) Lipase ✔
(b) Proteases
(c) Pepsin
(4) Trypsin

2. Fill in the blanks:
(i) There are two types of metabolic reactions.
(ii) Enzymes catalyze chemical reaction by lowering the activation energy.
(iii) Presence of enzyme does not affect the nature or properties of end products.
(iv) In constructive reaction large molecules are formed.
(v) Activity of enzymes can be enhanced by activator.
(vi) Small portion of enzyme where substrate attach with enzyme called active site.
(vii) Enzyme activity decreased by inhibitors.
(viii) As temperature increases, initially the rate of reaction will increase.
(ix) Enzyme changes in pH can cause enzymes to denature.
(x) In the human body there are more than 1000 known enzymes.
11. Reactions occur in living organisms called metabolic reaction.
12. Anabolism reactions are constructive reactions.
13. Catabolic reactions are destructive reactions.
14. The biochemical reaction requires high amount activation energy.
15. The molecules which facilitate biochemical reaction by reducing activation energy called enzymes.
16.Activity of Enzymes can be Enhanced by activator and declined by inhibitors.
17. Many enzymes are used commercially in industries, like paper, food, brewery, bio-detergents industries.
18. The enzymes attach with Substrate form enzymes substrate complex (ESC) after completion enzyme detached while product is formed.
19. There are two models to explain enzyme action: (i) Lock and Key model (ii) Induce fit model.