The Lineweaver-Burk plots in this figure represent the activities of enzymes in the absence and presence of different types of inhibitors. Which one represents the activity of the enzyme in the presence and absence of a mixed inhibitor? (choose the one best answer).
The Lineweaver-Burk plots in this figure represent the activities of enzymes in the absence and presence of different types of inhibitors. Which one represents the activity of the enzyme in the presence and absence of a mixed inhibitor? (choose the one best answer).
Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
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Transcribed Image Text:### Enzyme Inhibition: Lineweaver-Burk Plots Quiz
The Lineweaver-Burk plots in this figure represent the activities of enzymes in the absence and presence of different types of inhibitors. Which one represents the activity of the enzyme in the presence and absence of a mixed inhibitor? (Choose the one best answer).
- O A
- O B
- O C
- O D
**Explanation:**
In enzyme kinetics, Lineweaver-Burk plots are used to analyze the type of inhibition affecting an enzyme's activity. Different inhibitors interact with the enzyme in various ways, altering its activity. A mixed inhibitor can bind to both the enzyme alone and the enzyme-substrate complex, impacting both the enzyme's active site and its shape or function.
To answer this question correctly, one should understand how the different curves on a Lineweaver-Burk plot look without inhibition, with competitive inhibition, noncompetitive inhibition, and mixed inhibition.
![**Enzyme Inhibition Lineweaver-Burk Plots**
In enzyme kinetics, Lineweaver-Burk plots are commonly used to illustrate how enzyme-catalyzed reactions are affected by inhibitors. Below are four panels labeled A, B, C, and D, each depicting different types of enzyme inhibition.
**Panel A: Competitive Inhibition**
- The graph represents the effects of increasing competitive inhibitor concentration.
- It is a plot of 1/V (inverse of reaction velocity) against 1/[S] (inverse of substrate concentration).
- Three lines are depicted:
- **α = 1** (no inhibitor) line is the baseline.
- **α = 2 and α = 4** lines show what happens as the inhibitor concentration increases.
- The y-axis represents 1/V and the x-axis represents 1/[S].
- As the concentration of inhibitor increases, the slope of the line increases, indicating a higher apparent K_M (Michaelis constant), while V_max (maximum velocity) remains unchanged.
**Panel B: Uncompetitive Inhibition**
- This panel demonstrates uncompetitive inhibition.
- Similar axes as Panel A: 1/V on the y-axis and 1/[S] on the x-axis.
- Lines of slopes are labeled for **α' = 1** (no inhibitor), **α' = 1.5**, and **α' = 2**.
- Unlike competitive inhibition, both the x-intercept (representing -1/K_M) and y-intercept (representing 1/V_max) change as the inhibitor concentration varies.
- The parallel nature of the lines indicates that both V_max and K_M decrease proportionally.
**Panel C: Mixed Inhibition**
- Mixed inhibition is depicted in this panel, showing a combination of both competitive and uncompetitive inhibition characteristics.
- Axes labels: 1/V on the y-axis and 1/[S] on the x-axis.
- Five lines indicate different levels of inhibition:
- **α = 1, α' = 1** (no inhibition)
- **α = 1.5, α' = 1.25**
- **α = 2, α' = 1.5**
- Involves changes in both the slope and the intercepts:
- The slope changes with increasing inhibitor concentration (as seen in competitive inhibition).
- Both intercepts (on the x and y axes) change](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F07b00a25-4bbc-4603-8563-821c16d74641%2F6241f763-ee43-45a6-96f4-21fd815e62f9%2Fgv4phu_processed.jpeg&w=3840&q=75)
Transcribed Image Text:**Enzyme Inhibition Lineweaver-Burk Plots**
In enzyme kinetics, Lineweaver-Burk plots are commonly used to illustrate how enzyme-catalyzed reactions are affected by inhibitors. Below are four panels labeled A, B, C, and D, each depicting different types of enzyme inhibition.
**Panel A: Competitive Inhibition**
- The graph represents the effects of increasing competitive inhibitor concentration.
- It is a plot of 1/V (inverse of reaction velocity) against 1/[S] (inverse of substrate concentration).
- Three lines are depicted:
- **α = 1** (no inhibitor) line is the baseline.
- **α = 2 and α = 4** lines show what happens as the inhibitor concentration increases.
- The y-axis represents 1/V and the x-axis represents 1/[S].
- As the concentration of inhibitor increases, the slope of the line increases, indicating a higher apparent K_M (Michaelis constant), while V_max (maximum velocity) remains unchanged.
**Panel B: Uncompetitive Inhibition**
- This panel demonstrates uncompetitive inhibition.
- Similar axes as Panel A: 1/V on the y-axis and 1/[S] on the x-axis.
- Lines of slopes are labeled for **α' = 1** (no inhibitor), **α' = 1.5**, and **α' = 2**.
- Unlike competitive inhibition, both the x-intercept (representing -1/K_M) and y-intercept (representing 1/V_max) change as the inhibitor concentration varies.
- The parallel nature of the lines indicates that both V_max and K_M decrease proportionally.
**Panel C: Mixed Inhibition**
- Mixed inhibition is depicted in this panel, showing a combination of both competitive and uncompetitive inhibition characteristics.
- Axes labels: 1/V on the y-axis and 1/[S] on the x-axis.
- Five lines indicate different levels of inhibition:
- **α = 1, α' = 1** (no inhibition)
- **α = 1.5, α' = 1.25**
- **α = 2, α' = 1.5**
- Involves changes in both the slope and the intercepts:
- The slope changes with increasing inhibitor concentration (as seen in competitive inhibition).
- Both intercepts (on the x and y axes) change
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