AIIMS MCAT AIPMT PMT JIPMER IBO Enzymes practice questions 2015

1. The figure given below shows the conversion of a substrate into product by an enzyme. In which one of the four options (a—d) the components of reaction labelled as A, B, C and D are identified correctly?

enzyme-substrate-reaction

A B C D
(a) Free energy Transition state Activation energy with enzyme Activation energy without enzyme
(b) Transition state Free energy Activation energy without enzyme Activation energy with enzyme
(c) Transition state Free energy Activation energy with enzyme Activation energy without enzyme
(d) Activation energy with enzyme Transition state Activation energy without enzyme Free energy

1. The figure given below shows the conversion of a substrate into product by an enzyme. In which one of the four options (a—d) the components of reaction labelled as A, B, C and D are identified correctly?2. Accumulation of glucose-6-phosphate inhibits the activity of enzyme glucohexokinase. This is an example of
(a) competitive inhibition
(b) allosteric inhibition
(c) both (a) and (b)
(d) none of these.
3. Enzymes differ from ordinary catalysts, because the enzymes consist of
(a) vitamins (b) non-proteins
(c) proteins (d) minerals.
4. Which of the following is required for enzyme action? [Km = Michaelis constant and Kt = Rate constant]
(a) Low Km value (b) High Km value
(c) Low K, value (d) High K, value
5. The protein part of an enzyme which works only in the presence of cofactors is called as
(a) apoenzyme (b) co-enzyme (c) prosthetic group (d) both (b) and (c).
6. Read the given statements and select the correct option.
Statement 1: Enzymes do not alter the overall change in free energy of a reaction.
Statement 2 : Enzymes are proteins whose three- dimensional structure is key to their functions.
(a) Both statements 1 and 2 are true and statement 2 is the correct explanation of statement 1.
(b) Both statements 1 and 2 are true but statement 2 is not the correct explanation of statement 1.
(c) Statement 1 is true and statement 2 is false.
(d) Both statements 1 and 2 are false.
7. Glutamate pyruvate transaminase belongs to which of the following categories of enzymes?
(a) Oxidoreductases (b) Hydrolases
(c) Lyases (d) Transferases
8. The temperature range, at which enzymes are maximum functional, is
(a) 30-55°C (b) 25-35°C
(c) 15-25°C (d) 40-65°C
9. The lock and key model of enzyme action illustrates that a particular enzyme molecule
(a) may be destroyed and resynthesized several times
(b) interacts with a specific type of substrate molecule
(c) reacts at identical rates under all conditions
(d) forms a permanent enzyme-substrate complex.
10. An example of competitive inhibition of an enzyme is the inhibition of
(a) succinate dehydrogenase by malonic acid
(b) cytochrome oxidase by cyanide
(c) hexokinase by glucose-6-phosphate
(d) carbonic anhydrase by carbon dioxide.
11. Michaelis-Menten constant (KJ of an enzyme is substrate concentration at which the reaction attains
(a) its maximum velocity
(b) half its maximum velocity
(c) double its maximum velocity
(d) its normal velocity.
12. The enzyme which is added to baby foods to partially pre-digest them is
(a) zymase (b) protease
(c) streptokinase (d) trypsin.
13. “All enzymes are proteins”. This statement is now modified because an apparent exception to this biological truth is
(a) restriction endonuclease
(b) dehydrogenase
(c) ribozyme
(d) nitroreductase.
14. A ribozyme is
(a) a proteinaceous enzyme
(b) a catalytic RNA
(c) an enzyme that helps in ribose synthesis
(d) an enzyme that joins ribose with adenine.
15. A competitive enzyme inhibitor
(a) increases Km without affecting Vmax
(b) decreases Km without affecting Vmax
(c) increases Vmai< without affecting Km
(d) decreases both Vmax and Km.
16. Nomenclature of an enzyme consists of
(a) first substrate name then reaction type
(b) first reaction type and then product name
(c) only reaction type
(d) only product name.
17. Which one of the following graphs shows the relationship between the velocity (V) of an enzymatic reaction and substrate concentration (S)?

velocity (V) of an enzymatic reaction and substrate concentration (S)

18. Feed back inhibition of enzyme action is affected by
(a) enzyme (b) substrate
(c) end product (d) none of these.
19. Select the correct substrate-enzyme pair out of the following.
(a) Casein-Rennin (b) Protein-Amylase (c) Carbohydrate-Lipase (d) Lactose-Maltase
20. Which category of enzymes are used to catalyze the given reaction?

(a) Transferases (b) Hydrolases 1
(c) Ligases (d) Lyases.

 21. Which statement regarding coenzyme is incorrect?
(a) Every coenzyme is a cofactor and every cofactor is a coenzyme.
(b) Every coenzyme is a cofactor but every cofactor is not a coenzyme.
(c) Most of the coenzymes are nucleotides and are composed of vitamins.
(d) Coenzymes are the active constituents of enzymes
(Punjab 2005)
22. Which enzyme is useful as colour brightening agent in detergent industry ?
(a) Amylase (b) Lipase
(c) Protease (d) Cellulase (Punjab 2005)
23. An organic substance bound to an enzyme and essential for its activity is called
(a) isoenzyme (b) coenzyme
(c) holoenzyme (d) apoenzyme.
(CBSE-PMT 2006)
24. Which enzyme converts glucose into alcohol?
(a) Invertase (b) Lipase
(c) Zymase (d) Diastase
(UP-CPMT 2008)
25. The effectiveness of an enzyme is affected least by
(a) temperature
(b) concentration of the substrate
(c) original activation energy of the system
(d) concentration of the enzyme. (DPMT 2009)
26.Enzymes that catalyse inter conversion of optical, geometrical or positional isomers are
(a) ligases (b) lyases
(c) hydrolases (d) isomerases
(DPMT 2009)
27. The protein part of a conjugated enzyme is
(a) holoenzyme (b) isoenzyme
(c) apoenzyme (d) co-enzyme. (AMU 2009)
28. An enzyme is a
(a) carbohydrate (b) lipid
(c) protein (d) DNA. (Odisha 2009)
29. Which one is the cofactor of carbonic anhydrase?
(a) Fe (b) Zn
(c) Cu (d) Mg (WB JEE 2010)
30. Which of the following statements is correct ?
(a) All enzymes are protein.
(b) All proteins are enzyme.
(c) All enzymes are not protein.
(d) All enzymes and hormones are protein.
(BHU 2010)
31. A particular enzyme molecule interacts with a specific substrate molecule is explained by
(a) enzyme-substrate concept
(b) activation energy concept
(c) destroyed and re-synthesised concept
(d) lock and key concept. (DUMET 2010)
32. Floloenzyme consists of
(a) enzyme protein and coenzyme
(b) only protein parts
(c) nucleic acid and enzymes
(d) only coenzyme. (Odisha 2010)
33. The curve given below shows enzymatic activity in relation to three conditions (pH, temperature and substrate concentration).

1

 

 

 

What do the x and y axis represent?
x-axis                                            y-axis
(a) enzymatic activity                pH
(b) temperature                          enzyme activity
(c) substrate concentration      enzymatic activity
(d) enzymatic activity                temperature
(AIPMT Prelims 2011)
34. The tightly bound non proteinaceous organic compound is
(a) prosthetic group (b) cofactor
(c) apoenzyme (d) holoenzyme.
(Odisha 2011)
35. Select the type of enzyme involved in the following reaction:

(a) dehydrogenase (b) transferase
(c) hydrolase (d) lyase
(e) isomerase (Kerala 2011)
36. Which one of the following is not true for enzymes?
(a) They act on a specific substrate.
(b) They are made up of fat and sugar.
(c) They act at a specific temperature.
(d) They act at a specific pH. (WB JEE 2012)
37. What is the substrate for lipase enzyme ?
(a) Protein (b) Carbohydrate
(c) Lipid (d) Nucleic acid
(WB JEE 2012)
38. Thermolabile protein part of enzyme is called
(a) proenzyme (b) holoenzyme
(c) apoenzyme (d) isoenzyme.
(Odisha 2012)
39. The molecules that are well recognized as biocatalysts in addition to enzymes are
(a) polysaccharides (b) fatty acids
(c) RNAs (d) none of these.
(AFMC 2012)
40. The essential chemical components of many coenzymes are
(a) carbohydrates (b) vitamins
(c) proteins (d) nucleic acids.
(NEET 2013)
41. Transition state structure of the substrate formed during a enzymatic reaction is
(a) transient and unstable
(b) permanent and stable
(c) transient but stable
(d) permanent but unstable. (NEET 2013)
42. Which of the following statements about enzymes is wrong?
(a) Enzymes are denatured at high temperatures.
(b) Enzymes are mostly proteins but some are lipids also.
(c) Enzymes are highly specific.
(d) Enzymes require optimum pH and temperature for maximum activity. (NEET-Karnataka 2013)
43. Which of the following is false with respect to prosthetic groups? These are
(a) proteins
(b) non-proteins
(c) tightly bound to enzymes
(d) metal compounds. (AMU 2013)
44. Select the option which is not correct with respect to enzyme action.
(a) Substrate binds with enzyme at its active site.
(b) Addition of lot of succinate does not reverse the inhibition of succinic dehydrogenase by malonate.
(c) A non – competitive inhibitor binds the enzyme at a site distinct from that which binds the substrate.
(d) Malonate is a competitive inhibitor of succinic dehydrogenase.
(AIPMT 2014)
45. An organic non-protein cofactor which is easily separable from the apoenzyme is called
(a) prosthetic group (b) coenzyme
(c) alloenzyme (d) all the above.
(AMU 2014)
46. Substrate of an enzyme is
(a) the reactant of the reaction catalysed by the enzyme
(b) competitive inhibitor of the enzyme
(c) uncompetitive inhibitor of the enzyme
(d) prosthetic group of the enzyme. (AM U 2014)
47. Which of the following statements regarding enzymes is not true?
(a) Enzymes lower the activation energy of a reaction.
(b) Enzymes speed up the attainment of equilibrium of the reaction.
(c) Enzyme change the value of equilibrium constant of the reaction.
(d) All the above. (AMU 2014)
48. Coenzymes NAD and NADP contain
(a) niacin (b) biotin
(c) thiamine (d) vitamin B12
(e) vitamin A. (Kerala PMT 2014)
49. Km is a
(a) product (b) enzyme
(c) constant (d) unit. (WB JEE 2014)
50. The protein component of a holoenzyme is known as
(a) coenzyme (b) cofactor
(c) prosthetic group (d) apoenzyme.
(WB JEE 2014)
Answers
1.(b) 2.(b) 3.(c) 4.(a)5.(a) 6. (b) 7. (d)    8. (b)   9. (b)  10. (a)
11. (b)  12. (d)  13. (c)  14. (b)  15. (a)  16. (a)  17. (d)  18. (c)  19. (a)  20. (d)
21. (a) 22. (d) 23. (b) 24. (c) 25. (c) 26. (d) 27. (c) 28. (c) 29. (b) 30.(c)
31. (d) 32. (a) 33. (b) 34. (a) 35. (b) 36. (b) 37. (c) 38. (c) 39. (c) 40.(b)
41. (a) 42. (b) 43. (a) 44. (b) 45. (b) 46. (a) 47. (c) 48. (a) 49. (c) 50. (d)  

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