MDCAT XI Biology Enzymes Online Test-2

681

Created on June 13, 2025 By

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📚 Test Details

Subject: Biology
Class: 1st year / XI
Chapter Name: Enzymes
Test: 2
Book: Sindh Textbook
Total No. Of MCQs: 50 MCQs
Time Allowed: 50 Minutes

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1 / 50

1. The conditions under which living cells carry on their life processes:

a) High temperature, low atmospheric pressure

b) Low temperature, very high atmospheric pressure

c) Low temperature, low atmospheric pressure

d) high temperature, high atmospheric pressure

2 / 50

2. Enzyme is a/an:

a) Greek word

b) Latin

c) Italic

d) GermanGerman

3 / 50

3. The term "enzyme" was coined by:

a) Friedrich in 1887

b) Thomas Cech in 1878

c) Friedrich in 1878

d) Thomas Cech in the 1980s

4 / 50

4. Molecules which catalyze reactions involved in processing genetic information to be used by a cell are called:

a) Riboenzyme

b) Conjugated enzyme

c) Ribozyme

d) Coenzyme

5 / 50

5. Which one of the following is correct?

a) Enzymes are synthesized in the cell

b) Enzymes are macromolecules of globular size

c) Enzymes are specific in nature and function

d) All

6 / 50

6. Enzyme activity can be accelerated by:

a) Ions

b) Salts

c) Mn, Mg, Cl⁻

d) All

7 / 50

7. Which one of the following is correct about enzymes?

a) They don't remain chemically unchanged during and after chemical reactions

b) They are inhibited by substrate concentration, enzyme concentration, pH, and temperature

c) They are smaller in size than the substrate

d) All

8 / 50

8. The region whose amino acids make temporary bonds with the substrate is called the:

a) Active site

b) Binding site

c) Catalytic site

d) Allosteric site

9 / 50

9. The non-protein part of an enzyme is called a:

a) Co-factor

b) Holoenzyme

c) Apoenzyme

d) Active site

10 / 50

10. Which one of the following is correct?

a) Metallic ions are detachable co-factors

b) Coenzymes are derivatives of vitamins

c) Prosthetic groups are covalently bonded and are a permanent part of the enzyme

d) All

11 / 50

11. A conjugated enzyme without its co-factor is called:

a) Apoenzyme

b) Holoenzyme

c) Prosthetic group

d) Vitamins

12 / 50

12. Which one of the following is not correct?

a) Apoenzyme works separately

b) An activated enzyme consists of a polypeptide chain and a co-factor, collectively called a holoenzyme

c) NAD and FAD are examples of coenzymes

d) None

13 / 50

13. Pepsinogen is inactive due to the presence of which chain at its active site?

a) Polypeptide

b) Peptone

c) Peptide

d) Insulin

14 / 50

14. The lock and key model was given by:

a) Emil Fischer

b) Koshland

c) Friedrich Wilhelm Kuhn

d) Thomas Cech and Sidney Altman

15 / 50

15. The lock and key model was proposed in:

a) 1889

b) 1898

c) 1878

d) 1959

16 / 50

16. The induced fit model was given by:

a) Emil Fischer in 1898

b) Emil Fischer in 1959

c) Koshland in 1898

d) Koshland in 1959

17 / 50

17. According to the lock and key model:

a) A particular enzyme acts on a particular substrate

b) This theory depends upon physical contact between the substrate and enzyme

c) Enzymes work with absolute specificity

d) All

18 / 50

18. Reactants must contain sufficient energy to overcome a barrier called:

a) Kinetic energy

b) Potential energy

c) Activation energy

d) Translational energy

19 / 50

19. Which one of the following is not correct?

a) The rate of enzyme activity means the quantity of substrate transformed into product in a minute

b) When an inhibitor binds to an enzyme away from the active site, the shape of the enzyme becomes altered; this is called an allosteric inhibitor

c) Molecules that bind to an enzyme away from the active site and increase its activity are called allosteric activators

d) None

20 / 50

20. Which one of the following is correct?

a) An increase of 10°C in temperature doubles the rate of reaction

b) Human enzymes are highly inactive at 37°C

c) A slight change in pH does not cause ionization of amino acids

d) All

21 / 50

21. Some bacteria that survive in hot springs are called thermophilic because they have an optimum temperature of:

a) 70°C or higher

b) 90°C or higher

c) 37°C or higher

d) 25°C to 42°C

22 / 50

22. The ATPase is an example of :

a) Nuclease enzyme

b) Nucleotidase enzyme

c) Phosphatase enzyme

d) Both A and B

23 / 50

23. Optimum pH of pepsin is:

a) 1.4

b) 1.5 to 2.5

c) 8.5

d) 7

24 / 50

24. The type of inhibition that occurs by molecules very similar to the substrate and that bind to the active site is called:

a) Competitive

b) Non-competitive

c) Uncompetitive

d) Anti-competitive

25 / 50

25. Penicillin is a competitive inhibitor that blocks the enzyme responsible for constructing the bacterial:

a) Cell membrane

b) Cell wall

c) Enzymes

d) Protein

26 / 50

26. It takes place when an enzyme inhibitor binds only to the complex formed between the enzyme and the substrate:

a) Competitive

b) Non-competitive

c) Uncompetitive

d) All

27 / 50

27. Enzymes can be classified on the basis of:

a) Types of reactions

b) Substrates on which they act

c) Saturation

d) A and B

28 / 50

28. Enzymes are classified based on the type of reactions they catalyze into how many groups?

a) 6

b) 10

c) 3

d) 7

29 / 50

29. These are digestive enzymes responsible for breaking bonds by H₂O:

a) Transferase

b) Lyase

c) Hydrolase

d) Ligase

30 / 50

30. These enzymes catalyze the breakdown of specific covalent bonds and the removal of groups without hydrolysis:

a) Hydrolase

b) Synthetase

c) Oxidoreductase

d) Lyase

31 / 50

31. Lipase performs:

a) Hydrolysis of fat

b) Hydrolysis of ATP

c) Hydrolysis of lactose

d) It is a regulatory enzyme and does not perform hydrolysis

32 / 50

32. Which one of the following is the correct sequence?
E= Enzyme , S=Substrate , P=Product

a) E + S → E/S → E + P → E/P

b) E + S → E/P → E/S → E + P

c) E + S → E + P → E/S → E/P

d) E + S → E/S → E/P → E + P

33 / 50

33. Which one of the following factors affect enzyme activity?

a) Temperature

b) pH

c) Radiation

d) All

34 / 50

34. An enzyme increases the speed of a reaction by:

a) Adding to activation energy requirements

b) Lowering activation energy requirements

c) Decreasing the concentration of products

d) Increasing the concentration of products

35 / 50

35. ___ is mostly a non-protein chemical compound that is required for a protein's biological activity (Past Paper):

a) Enzyme

b) Cofactor

c) Substrate

d) Active site

36 / 50

36. Which one of the following is a characteristic of all catalysts?

a) They are broken down in a reaction

b) They are made up of protein

c) They are not changed by the reaction

d) They cannot change the rate of reaction

37 / 50

37. The specificity of enzymes is due to their:

a) High molecular weight

b) pH sensitivity

c) Hydrogen bonding

d) Surface configuration

38 / 50

38. When a prosthetic group joins with an enzyme, it forms a:

a) Cofactor

b) Holoenzyme

c) Coenzyme

d) Apoenzyme

39 / 50

39. Some enzymes require the presence of a non-protein molecule to behave catalytically. An enzyme devoid of this molecule is called a:

a) Holoenzyme

b) Apoenzyme

c) Coenzyme

d) Zymoenzyme

40 / 50

40. Which one of the following is not an enzyme? (Past Paper)

a) Polymerase

b) Isomerase

c) Enzymate

d) Hydrolase

41 / 50

41. A holoenzyme consists of:

a) Apoenzyme and prosthetic group

b) Proenzymes and prosthetic group

c) Coenzyme and prosthetic group

d) Cofactor and coenzyme

42 / 50

42. Enzymes that consist only of protein:

a) Amylase

b) Pepsin

c) Both A and B

d) Acetyl CoA

43 / 50

43. Enzymes that act within the same cell where they are produced are called:

a) Endoenzyme

b) Exoenzyme

c) Intracellular

d) Intercellular

44 / 50

44. In Acetyl Coenzyme A, the Coenzyme A (a sulfur-containing compound) is derived from:

a) Vitamin A

b) Vitamin D

c) Vitamin B

d) Vitamin C

45 / 50

45. A coenzyme constitutes approximately what percentage of the entire enzyme?

a) 5%

b) 10%

c) 99%

d) 1%

46 / 50

46. Feedback is affected by the:

a) End product

b) First product

c) Substrate

d) Enzyme itself

47 / 50

47. The Specificty of enzymes is due to ____

a) their higher molecular weight

b) their hydrogen binding

c) their pH sensitivity

d) their surface configuration

48 / 50

48. A 25-year-old woman is prescribed penicillin for a Streptococcus pyogenes throat infection. Penicillin functions by binding to and inhibiting the transpeptidase enzyme, which is essential for bacterial cell wall synthesis. This inhibition prevents the cross-linking of peptidoglycan strands, leading to bacterial lysis.

Further studies reveal that penicillin resembles the D-Ala-D-Ala terminus of the natural substrate of transpeptidase and binds to the active site of the enzyme.

Which of the following best describes the mechanism of action of penicillin?

a) Uncompetitive inhibition of peptidoglycan polymerase

b) Irreversible competitive inhibition of transpeptidase

c) Reversible competitive inhibition of ribosomal enzymes

d) Allosteric modulation of cell membrane proteins

49 / 50

49.

Which statement is true for a non-competitive inhibitor of enzyme activity, but not for a com-petitive inhibitor?

a) Inhibitor molecules are similar to normal substrate molecules in size and shape.

b) Inhibition can be reduced by increasing the concentration of substrate molecules.

c) Large numbers of inhibitor molecules are needed for effective enzyme inhibition.

d) The inhibitor binds to the enzyme molecule at a position away from the active centre

50 / 50

50. Which statement correctly describes a possible action of a competitive enzyme inhibitor?

a) It binds at the active site and prevents the formation of an enzyme-substrate complex.

b) It binds near the active site and prevents the formation of an enzyme-substrate com-plex.

c) It binds near an allosteric site and prevents the formation of an enzyme-substrate com-plex.

d) It binds to an allosteric site and prevents the formation of an enzyme-substrate com-plex.

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MDCAT XI Biology Enzymes Online Test-2

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