Questions and Answers
What is the mechanism of competitive inhibition?
What is the characteristic that allows competitive inhibition to be overcome by increasing substrate concentration?
What is the term for inhibition that occurs when an inhibitor binds to the E-S complex?
Which type of inhibition involves a conformational change to the enzyme's active site?
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What is the main difference between competitive and non-competitive inhibition?
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What is the term for inhibition that occurs when an inhibitor binds to a site other than the active site?
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What happens to the rate of reaction when all of the substrate is bound to enzymes?
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What is the effect of increasing substrate concentration on the rate of reaction?
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What happens to an enzyme when it is denatured?
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What can cause denaturation of an enzyme?
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What do enzyme inhibitors do?
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What type of inhibitors occupy the active sites by forming covalent bonds or physically block the active sites?
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How do reversible inhibitors attach to enzymes?
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What can be done to eliminate reversible inhibitors from an enzyme?
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What is the primary theory that explains the high specificity of enzymes?
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What does the term 'denaturation' refer to in the context of enzymes?
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Which of the following factors directly influences the rate of an enzyme-catalyzed reaction?
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How does the Induced Fit Theory differ from the Key and Lock Theory?
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What is the effect of increasing the enzyme concentration on the rate of an enzyme-catalyzed reaction?
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What happens to the rate of an enzyme-catalyzed reaction as the substrate concentration decreases?
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Which of the following statements about the pH optimum of an enzyme is TRUE?
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What is the primary function of the active site of an enzyme?
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Study Notes
Mechanism of Enzyme Action
- Enzymes are highly specific, with their active site complementary in conformation to the substrate, allowing for precise binding.
- The Key and Lock (Fischer) Theory proposes a fixed active site shape that recognizes the substrate.
- The Induced Fit Theory (Khoshland) suggests a flexible active site that changes shape to accommodate the substrate, allowing for a closer fit.
Rate of Enzyme Reactions
- The rate of enzyme reaction is measured by the amount of substrate converted or product formed over time.
- The rate is determined by the slope of the tangent to the curve in the initial stage of the reaction.
- Increasing temperature generally speeds up the reaction, but extreme temperatures can cause enzyme denaturation.
- Each enzyme has an optimum pH range, and changing the pH outside of this range slows down the reaction.
- Increasing enzyme concentration speeds up the reaction, as long as there is available substrate to bind to.
- Increasing substrate concentration also increases the rate of reaction, but only up to a certain point, after which additional substrate has no effect.
Denaturation
- Denaturation occurs when the hydrogen bonds within an enzyme are broken, causing it to unfold or change shape.
- Denatured enzymes do not function properly due to changes in the active site shape.
- Causes of denaturation include heat, changes in pH, heavy-metal ions, organic solvents, and UV radiation.
Enzyme Inhibitors
- Enzyme inhibitors are chemicals that bind to an enzyme and prevent the formation of an enzyme-substrate complex.
- Inhibitors can be classified as reversible or irreversible.
- Reversible inhibitors attach to enzymes via non-covalent interactions and can be easily eliminated by dilution or dialysis.
- Irreversible inhibitors form covalent bonds or physically block the active site, permanently blocking enzyme activity.
Types of Inhibition
- Competitive inhibition: inhibitor binds to the active site, preventing substrate binding, and can be reduced by increasing substrate concentration.
- Non-competitive inhibition: inhibitor binds to an allosteric site, causing a conformational change that prevents substrate binding, and cannot be reduced by increasing substrate concentration.
- Uncompetitive inhibition: inhibitor binds only to the enzyme-substrate complex, preventing substrate binding.
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Description
This lecture explains the mechanism of enzyme action, including the key and lock theory, and how enzymes are very specific in their action. It's part of a biochemistry course taught by Dr. Wael Sobhy Darwish.
