Table of contents

1. Introduction to Biochemistry4h 34m
2. Water3h 23m
3. Amino Acids8h 10m
4. Protein Structure10h 4m
5. Protein Techniques14h 5m
6. Enzymes and Enzyme Kinetics13h 38m
7. Enzyme Inhibition and Regulation 8h 42m
8. Protein Function 9h 41m
9. Carbohydrates7h 49m
10. Lipids5h 49m
11. Biological Membranes and Transport 6h 37m
12. Biosignaling9h 45m
Review 1: Nucleic Acids, Lipids, & Membranes2h 47m
Review 2: Biosignaling, Glycolysis, Gluconeogenesis, & PP-Pathway3h 12m
Review 3: Pyruvate & Fatty Acid Oxidation, Citric Acid Cycle, & Glycogen Metabolism2h 26m
Review 4: Amino Acid Oxidation, Oxidative Phosphorylation, & Photophosphorylation1h 48m

7. Enzyme Inhibition and Regulation

Enzyme Inhibition

Biochemistry

7. Enzyme Inhibition and Regulation

Enzyme Inhibition

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Multiple Choice

How does a noncompetitive inhibitor decrease the rate of an enzyme-catalyzed reaction?

It increases the enzyme's affinity for the substrate, thereby decreasing $K_m$.

It competes with the substrate for binding at the active site, increasing the apparent $K_m$ but not affecting $V_{max}$.

It binds to an allosteric site on the enzyme, reducing the maximum velocity ($V_{max}$) without affecting the substrate's binding affinity ($K_m$).

It binds irreversibly to the enzyme's active site, permanently inactivating the enzyme.

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Verified step by step guidance

Understand the concept of enzyme inhibition: Noncompetitive inhibitors bind to an allosteric site on the enzyme, which is a site other than the active site. This binding alters the enzyme's structure or function, reducing its catalytic efficiency.

Recognize the key distinction between noncompetitive inhibition and other types of inhibition: Unlike competitive inhibitors, noncompetitive inhibitors do not compete with the substrate for the active site. Therefore, the substrate's binding affinity ($K_m$) remains unchanged.

Analyze the effect on reaction kinetics: Noncompetitive inhibitors decrease the maximum velocity ($V_{max}$) of the enzyme-catalyzed reaction because they reduce the number of functional enzyme molecules available for catalysis. This occurs regardless of substrate concentration.

Understand why $K_m$ is unaffected: Since the inhibitor does not interfere with substrate binding at the active site, the enzyme's affinity for the substrate remains constant, and $K_m$ is not altered.

Summarize the mechanism: Noncompetitive inhibitors bind to an allosteric site, causing a conformational change in the enzyme that reduces its catalytic activity. This results in a lower $V_{max}$ while leaving $K_m$ unchanged.