7: Enzyme Kinetics

Students determine Vmax and Km from substrate concentration data, interpret Michaelis-Menten and Lineweaver-Burk plots, and calculate enzyme efficiency using kcat.

LibreTexts reference: Unit 2, Chapter 2: Enzyme Kinetics

True/False Statements About Michaelis-Menten Kinetics

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Which one of the following statements is FALSE of Michaelis-Menten kinetics?

• A. M-M kinetics assumes that the product is NOT available and there is no measureable reverse reaction rate.
• B. The reaction rate is proportional to the substrate concentration.
• C. M-M kinetics assumes that the enzyme bound to the product [EP] is short lived and does NOT contribute to the reaction rate.
• D. When the substrate concentration, [S], is much smaller than K_M, the reaction rate is linear.
• E. M-M kinetics was developed by American linguist Laura Michaelis and Belgian cyclist Milan Menten in 1913.

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Michaelis-Menten Constant (Km) from Enzyme Activity Data

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Michaelis-Menten question. The following question refers to the table (below) of enzyme activity.

substrate concentration, [S]	initial reaction velocity V0
0.001	80.0
0.002	106.7
0.005	133.4
0.010	145.5
0.020	152.4
0.050	156.9
0.100	158.5
0.200	159.3
0.500	159.7
1.000	159.9
2.000	160.0

Using the table (above), calculate the value for the Michaelis-Menten constant, K_M.

• A. K_M = 0.001 mM
• B. K_M = 0.010 mM
• C. K_M = 0.020 mM
• D. K_M = 0.050 mM
• E. K_M = 0.100 mM

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Optimal Enzyme Activity Conditions (Type 1)

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Enzyme	Effective Temperature Range (°C)	Optimum pH
A	75–85	7.0
B	30–40	2.0
C	60–75	5.0
D	50–58	10.0

If enzyme D is currently functioning at 39°C and a pH of 10.
Which one of the following conditions would increase the rate of enzyme activity

• A. The temperature is decreased to 34°C and the pH is kept the same.
• B. The temperature is kept the same and the pH is increased to 12.0.
• C. The temperature is increased to 53°C and the pH is kept the same.
• D. The temperature is kept the same and the pH is decreased to 9.0.

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Optimal Enzyme Activity from Temperature and pH (Type 2)

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Enzyme	Effective Temperature Range (°C)	Optimum pH
A	20–30	3.0
B	35–45	10.0
C	70–78	1.0
D	50–62	5.0

Which one of the enzymes would be most active under the following conditions?
The temperature is 37°C and the pH is 9.8.

• A. Enzyme A
• B. Enzyme B
• C. Enzyme C
• D. Enzyme D

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Optimal Enzyme Activity from Temperature and pH (Type 3)

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Enzyme	Effective Temperature Range (°C)	Optimum pH
A	50–62	8.0
B	75–85	5.0
C	30–48	2.0
D	65–75	10.0

Under which one of the following conditions would enzyme D be most active?

• A. The temperature is 84°C and the pH is 8.5.
• B. The temperature is 54°C and the pH is 8.0.
• C. The temperature is 71°C and the pH is 9.8.
• D. The temperature is 81°C and the pH is 12.0.
• E. The temperature is 56°C and the pH is 12.5.

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