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 regarding Michaelis-Menten kinetics?

• A. M-M kinetics was developed by German biochemist Leonor Michaelis and Canadian physician Maud Menten in 1913.
• B. The reaction rate is proportional to the substrate concentration.
• C. M-M kinetics assumes that the concentration of enzyme-substrate complex [ES] is constant.
• D. When the substrate concentration, [S], is much smaller than K_M, the reaction rate is linear.
• E. M-M kinetics assumes that the enzyme-substrate complex [ES] is short lived and does NOT contribute to the reaction rate.

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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	0.8
0.002	1.6
0.005	3.7
0.010	6.7
0.020	11.5
0.050	20.0
0.100	26.7
0.200	32.0
0.500	36.4
1.000	38.1
2.000	39.1
5.000	39.7
10.000	39.9
20.000	40.0

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

• A. K_M = 0.001 mM
• B. K_M = 0.002 mM
• C. K_M = 0.010 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	5.0
B	15–23	1.0
C	55–67	9.0
D	45–60	7.0

If enzyme D is currently functioning at 38°C and a pH of 7.
Which one of the following conditions would increase the rate of enzyme activity

• A. The temperature is increased to 54°C and the pH is kept the same.
• B. The temperature is kept the same and the pH is increased to 9.0.
• C. The temperature is kept the same and the pH is decreased to 5.5.
• D. The temperature is decreased to 27°C and the pH is kept the same.

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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	55–73	3.0
B	35–45	1.0
C	75–83	9.0
D	20–30	6.0

Which one of the enzymes would be most active under the following conditions?
The temperature is 29°C and the pH is 6.2.

• 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	60–72	3.0
B	45–55	7.0
C	35–53	9.0
D	15–25	5.0

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

• A. The temperature is 34°C and the pH is 7.5.
• B. The temperature is 3°C and the pH is 7.5.
• C. The temperature is 38°C and the pH is 4.6.
• D. The temperature is 20°C and the pH is 4.6.
• E. The temperature is 24°C and the pH is 3.5.

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