Biochemistry Test Bank – Topic 2

Biochemistry Test Bank – Topic 2In every slide, you will find a question with 2 – 5 choices.

The answers of the questions will be in the last slide, so don’t forget to write your answers (To check them 💪).

1. KM, the Michaelis constant, is defined as that concentration of substrate at which enzyme is working at maximum velocity:

A. True.

B. False.

2. KM, the Michaelis constant is defined as the dissociation constant of the enzyme-substrate complex:

A. True.

B. False.

3. When the velocity of enzyme activity is plotted against substrate concentration, which of the following is obtained?

A. Hyperbolic curve.

B. Parabola.

C. Straight line with positive slope.

D. Straight line with negative slope.

4. Which of the following is the correct Line weaver-Burk equation?

A.1

𝑉0=

𝐾𝑀

𝑉𝑀𝑎𝑥[𝑆]+

1

𝑉𝑀𝑎𝑥

B.1

𝑉𝑀𝑎𝑥=

𝐾𝑀

𝑉0 𝑆+

1

𝑉0

C. 𝑉0 =𝑉𝑀𝑎𝑥 𝑆

𝐾𝑀+ 𝑆

D. 𝑉𝑀𝑎𝑥 =𝑉0 𝑆

𝐾𝑀 𝑆

5. The catalytic efficiency of two distinct enzymes can be compared based on which of the following factor?

A. KM.

B. Product formation.

C. Size of the enzymes.

D. pH of optimum value.

6. From the Lineweaver-Burk plot, the X-axis experimental data are expressed as:

A. 1/V.

B. V.

C. 1/S.

D. S.

7. In enzyme kinetics KM implies:

A. The substrate concentration that gives one half Vmax.

B. The dissocation constant for the enzyme substrate comples.

C. Concentration of enzyme.

D. Half of the substrate concentration required to achieve Vmax.

8. What is enzyme kinetics?

A. Study of [S].

B. Study of rate of reaction.

C. Study of initial velocity.

D. All of the above.

9. What is the effect on initial velocity if the substrate concentration is low?

A. Increases rapidly.

B. Increases slowly.

C. Decreases.

D. Remains constant.

10. What is the effect on initial velocity if the substrate concentration is high?

A. Increases rapidly.

B. Increases slowly.

C. Decreases.

D. Remains constant.

11. In how many forms, enzymes exists in an enzymatic reaction?

A. 1.

B. 2.

C. 3.

D. 4.

12. In which form the enzyme exists when the maximum velocity is observed?

A. E form.

B. ES form.

C. Both.

D. None.

13. When the reaction reaches its plateau state, which type of kinetics is seen?

A. Zero order kinetics.

B. First order kinetics.

C. Second order kinetics.

D. None of the above.

14. Turnover number is also known as?

A. Km.

B. Kcat.

C. K1.

D. K-1.

15. In which condition, V0=Vmax?

A. Low [S].

B. High [S].

C. Low V0.

D. High V0.

16. Which of the following statement is NOT true?

A. Turnover number is also known as catalytic constant.

B. The reaction for the formation of ES is irreversible.

C. The reaction is in steady state when rate of synthesis is equal to rate of degradation.

D. Plateau is called Vmax.

17. Which of the following is the slope of double-reciprocal plot?

A. Km/V0.

B. Vmax/Km.

C. -1/Km.

D. None of the above.

18. Which of the following terms are involved in Michaelis-Menten Equation?

A. Vmax.

B. Km.

C. V0.

D. All of the above.

19. The point at which the line intersects the y-axis of double-reciprocal plot is numerically equal to?

A. Km/V0.

B. Vmax/Km.

C. -1/Km.

D. 1/Vmax.

20. When [S]=KM, the velocity of an enzyme catalyzed reaction is about:

A. 0.1*VMAX.

B. 0.2*VMAX.

C. 0.3*VMAX.

D. 0.5*VMAX.

E. 0.9*VMAX.

21. The substrate KM in an enzyme-catalyzed reaction:

A. is usually less than Kd, the dissociation constant.

B. is never less than Kd.

C. cannot be equal to Kd.

D. is estimated from the Y-intercept of a Lineweaver-Burk plot.

E. cannot be derived from simple rate equations.

22. In an enzyme catalyzed reaction, __________ provides information on __________ and __________ provides information on __________.

A. KM, chemical step, VMAX, substrate binding.

B. VMAX, chemical step, kCAT, substrate binding.

C. KD, substrate binding, kCAT, chemical step.

D. KM, substrate binding, VMAX, chemical step.

E. kCAT, substrate binding, VMAX, chemical step.

23. The initial velocity, Vo, of an enzyme catalyzed reaction reaches Vmax:

A. At [S] = KM.

B. At [S] = 10*KM.

C. At 1/[S] = 1/KM.

D. Only as 1/[S] = 0.

E. The third and fourth choices are both correct.

24. The __________ of a double reciprocal plot equals __________ and the __________ equals __________.

A. slope, VMAX, y-intercept, KM.

B. slope, KM, y-intercept, 1/VMAX.

C. slope, KM/VMAX, y-intercept, 1/VMAX.

D. slope, KM/VMAX, y-intercept, VMAX.

E. slope, KM/VMAX, x-intercept, VMAX.

25. When [S] = 0.1*KM, the velocity of an enzyme catalyzed reaction is about:

A. 0.1*Vmax.

B. 0.3*Vmax.

C. 0.5*Vmax.

D. 0.7*Vmax.

E. 0.9*Vmax.

26. When [S] = 10*KM, the velocity of an enzyme catalyzed reaction is about:

A. 0.1*Vmax.

B. 0.3*Vmax.

C. 0.5*Vmax.

D. 0.7*Vmax.

E. 0.9*Vmax.

27. For an enzyme that displays Michaelis-Menten kinetics, the reaction velocity (as a fraction of Vmax ) observed at [S] = 2 KM will be:

A. 0.09.

B. 0.33.

C. 0.66.

D. 0.91.

28. Read the informative box below, and answer the question:

A. 1.5 min.

B. 3 min.

C. 6 min.

D. 13.5 min.

E. 27 min.

An enzyme-catalyzed reaction was carried out with

the substrate concentration initially 1,000 times

greater than the Km for that substrate. After 9

minutes, 1% of the substrate had been converted to

product, and the amount of product formed in the

reaction mixture was 12 µmol. If, in a separate

experiment, one-third as much enzyme and twice as

much substrate had been combined, how long

would it take for the same amount (12 µmol) of

product to be formed?

***Note: Use this link to know how to solve this question.

29. How can the Michaelis-Menten constant, Km, be derived from this Lineweaver-Burk plot?

A. Km = (-1) * (x-intercept).

B. Km = (slope).

C. Km = (slope) * (1/y-intercept).

D. Km = 1 / (x-intercept).

30. What relative values of Km and kcat would describe an enzyme with a high catalytic efficiency?

A. Low Km, low Kcat.

B. High Km, high Kcat.

C. Low Km, high Kcat.

D. High Km, low Kcat.

31. Read the informative box below, and answer the question:

A. 25 μM.

B. 50 μM.

C. 100 μM.

D. 250 μM.

E. 475 μM.

Assume that the reaction catalyzed by an enzyme

follows Michaelis-Menten kinetics. The substrate

concentration (Km, Michaelis constant) needed to

reach 50% of the maximum reaction velocity

(Vmax) is 25 μM. What substrate concentration is

required to obtain at least 95% of the maximum

reaction velocity?

***Note: Use this link to know how to solve this question.

32. Read the informative box below, and answer the question:

A. 2 nM.

B. 5 nM.

C. 10 nM.

D. 50 nM.

E. 100 nM.

Assume that the reaction catalyzed by an enzyme

follows Michaelis-Menten kinetics. If at a substrate

concentration of 100 nM, the reaction proceeds at

98% of the maximum reaction velocity (Vmax),

what is the Michaelis constant (Km) for this

substrate. Km is the substrate concentration

needed to reach 50% of Vmax.

33. The following ranking of substrates is in terms of affinity. Which one of these substrates has the highest Km?

A. D-Glucose.

B. ATP.

C. D-Fructose.

D. Can’t be determined.

D-Glucose > ATP > D-Fructose.

34. Read the informative box below, The KM of the enzyme is higher for:

A. A.

B. B.

C. Neither.

D. Can’t tell from this information.

The enzyme trypsin hydrolyzes peptides at the carboxyl side of Arg and Lys

residues. However, the amino acid residue that follows the Arg or Lys can

influence either the KM or the kcat of the reaction. Suppose that the

adjacent curves were generated by comparing two substrates for trypsin:

o Substrate A = Ser-Val-Arg-Pro.

o Substrate B = Ser-Val-Arg-Phe.

35. Read the informative box below, The enzyme binds:

A. More tightly to A.

B. More tightly to B.

C. Same to both.

D. Can’t tell.

The enzyme trypsin hydrolyzes peptides at the carboxyl side of Arg and Lys

residues. However, the amino acid residue that follows the Arg or Lys can

influence either the KM or the kcat of the reaction. Suppose that the

adjacent curves were generated by comparing two substrates for trypsin:

o Substrate A = Ser-Val-Arg-Pro.

o Substrate B = Ser-Val-Arg-Phe.

36. Read the informative box below, the approximate KM for Substrate A is:

A. 0.0001 M.

B. 0.0005 M.

C. 0.001 M.

D. >0.002 M.

The enzyme trypsin hydrolyzes peptides at the carboxyl side of Arg and Lys

residues. However, the amino acid residue that follows the Arg or Lys can

influence either the KM or the kcat of the reaction. Suppose that the

adjacent curves were generated by comparing two substrates for trypsin:

o Substrate A = Ser-Val-Arg-Pro.

o Substrate B = Ser-Val-Arg-Phe.

37. Read the informative box below, The kcat of the enzyme is higher for:

A. A.

B. B.

C. Neither.

D. Can’t tell from this information.

The enzyme trypsin hydrolyzes peptides at the carboxyl side of Arg and Lys

residues. However, the amino acid residue that follows the Arg or Lys can

influence either the KM or the kcat of the reaction. Suppose that the

adjacent curves were generated by comparing two substrates for trypsin:

o Substrate A = Ser-Val-Arg-Pro.

o Substrate B = Ser-Val-Arg-Phe.

38. What is the correct calculation for the rate of an enzyme reaction?

A. Amount of substrate used ÷ time taken.

B. Amount of substrate used + time taken.

C. Amount of substrate used × time taken.

39. Given the reaction of an enzyme that follows Michaelis-Menten kinetics, What is the initial reaction velocity at a substrate concentration of 30 mM?

A. 10 μM min-1.

B. 15 μM min-1 .

C. 30 μM min-1 .

D. 60 μM min-1 .

40. Read the informative box below, Vmax is equal to:

A. 0.1 (µM/min)-1.

B. 10 (µM/min)-1.

C. 0.1 µM/min.

D. 10 µM/min.

You measure the kinetics of an enzyme E as a function of substrate

concentration first without any inhibitor (see Table) and plot the data

using the double-reciprocal (Lineweaver-Burk) plot (Figure below). The

enzyme concentration is maintained constant at a level of 1 µM (=10-6 M).

41. Read the informative box below, Km is equal to:

A. 0.05 µM.

B. 0.5 µM.

C. 5 µM.

D. 50 µM.

E. 500 µM.

You measure the kinetics of an enzyme E as a function of substrate

concentration first without any inhibitor (see Table) and plot the data

using the double-reciprocal (Lineweaver-Burk) plot (Figure below). The

enzyme concentration is maintained constant at a level of 1 µM (=10-6 M).

42. Read the informative box below, Kcat is equal to:

A. 5 min-1.

B. 10 min-1.

C. 20 min-1 .

D. Can’t be determined.

You measure the kinetics of an enzyme E as a function of substrate

concentration first without any inhibitor (see Table) and plot the data

using the double-reciprocal (Lineweaver-Burk) plot (Figure below). The

enzyme concentration is maintained constant at a level of 1 µM (=10-6 M).

43. Which letter is drawn next to the arrow representing the difference in activation energy between the catalyzed and noncatalyzed reaction?

A. A.

B. B.

C. C.

D. D.

44. The turnover number of an enzyme is calculated by dividing the maximal velocity by the enzyme concentration.

A. True.

B. False.

45. In a Lineweaver-burk plot, the Y-intercept is -1/KM.

A. True.

B. False.

The key answers

Question No. Answers Question No. Answers Question No. Answers Question No. Answers Question No. Answers

1. B 10. B 19. D 28. E 37. A

2. B 11. B 20. D 29. C 38. A

3. A 12. B 21. B 30. C 39. C

4. A 13. A 22. D 31. E 40. D

5. A 14. B 23. D 32. A 41. C

6. C 15. B 24. C 33. C 42. B

7. A 16. B 25. A 34. B 43. C

8. B 17. D 26. E 35. A 44. A

9. A 18. D 27. C 36. A 45. B