Enzyme Action Mechanism and Factors
45 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What distinguishes irreversible inhibitors from other types of inhibitors?

  • They covalently modify the enzyme. (correct)
  • They increase the Km value of substrates.
  • They temporarily inhibit enzyme activity.
  • They can be easily reversed by increasing substrate concentration.

Which effect can result from the inhibition of acetylcholinesterase by diisopropyl fluorophosphate (DFP)?

  • Paralysis or death. (correct)
  • Enhanced muscle activity.
  • Increased nerve impulse transmission.
  • Improved enzymatic functioning.

What is a common therapeutic application of enzyme inhibitors?

  • To increase the effectiveness of all enzymes.
  • To promote enzyme activity in tumor cells.
  • To reduce the toxicity of antiviral drugs.
  • To lower arterial blood pressure through ACE inhibition. (correct)

Which class of drugs is exemplified by captopril, an enzyme inhibitor?

<p>Antihypertensive agents (D)</p> Signup and view all the answers

Which of the following statements about enzyme inhibitors is true?

<p>Certain synthetic drugs act as enzyme inhibitors with limited toxicity. (B)</p> Signup and view all the answers

What does Vmax represent in the Michaelis–Menten equation?

<p>The maximum velocity obtainable by the reaction (A)</p> Signup and view all the answers

Why is Km important in enzyme kinetics?

<p>It reflects the binding affinity of the enzyme for its substrate (C)</p> Signup and view all the answers

How does a high Km value affect enzyme-substrate binding affinity?

<p>It indicates low binding affinity (B)</p> Signup and view all the answers

What type of curve is derived from plotting Vo against [S] in enzyme kinetics?

<p>Hyperbolic curve (D)</p> Signup and view all the answers

What information can be obtained from a Lineweaver–Burk plot?

<p>Exact values of Vmax and Km (D)</p> Signup and view all the answers

What happens to an enzyme when the temperature increases significantly?

<p>It is denatured and loses its catalytic activity. (C)</p> Signup and view all the answers

What does a low Km value indicate about an enzyme-substrate pair?

<p>The enzyme binds to the substrate with high affinity (B)</p> Signup and view all the answers

How does a change in pH affect enzyme activity?

<p>It can denature the enzyme at extreme pH levels. (B)</p> Signup and view all the answers

Which statement describes the measurement of Vo in enzyme kinetics?

<p>It is measured during the first few minutes of reaction (D)</p> Signup and view all the answers

Which statement is true regarding enzyme concentration and substrate concentration?

<p>Increased enzyme concentration can increase the reaction rate when substrate is unlimited. (C)</p> Signup and view all the answers

What occurs as the substrate concentration increases past the saturation point?

<p>The reaction rate remains constant despite additional substrate. (B)</p> Signup and view all the answers

What effect does increasing substrate concentration have on the reaction rate until Vmax is reached?

<p>The reaction rate increases until a saturation point (B)</p> Signup and view all the answers

What effect can accumulating end-products have on enzyme activity?

<p>They can cause a change in the surrounding pH. (D)</p> Signup and view all the answers

How do enzymes function at low concentrations?

<p>They can catalyze reactions multiple times due to reusability. (B)</p> Signup and view all the answers

Which of the following describes an effect of temperature on enzyme function?

<p>Extreme temperatures can lead to denaturation of the enzyme. (A)</p> Signup and view all the answers

What is a consequence of changing the pH outside an enzyme's optimum range?

<p>It can lead to a loss of activity due to denaturation. (B)</p> Signup and view all the answers

What is the effect of uncompetitive inhibitors on the enzyme's efficiency?

<p>They decrease both Km and Vmax. (A)</p> Signup and view all the answers

How does the binding of an inhibitor at a site other than the active site affect the enzyme?

<p>It may change the enzyme's shape, affecting substrate binding. (A)</p> Signup and view all the answers

What distinguishes irreversible inhibitors from other types of enzyme inhibitors?

<p>They permanently alter the enzyme's structure. (D)</p> Signup and view all the answers

What happens to Vmax and Km when an irreversible inhibitor is present?

<p>Vmax decreases while Km remains unchanged. (D)</p> Signup and view all the answers

Which of the following statements about the double reciprocal plot for uncompetitive inhibition is correct?

<p>It displays parallel lines to that of the uninhibited enzyme. (A)</p> Signup and view all the answers

Heavy metal ions like mercury affect enzyme activity by:

<p>Breaking disulphide bonds and altering enzyme shape. (C)</p> Signup and view all the answers

In non-competitive inhibition, how does the inhibitor interact with the enzyme?

<p>It can bind to both the enzyme and the enzyme-substrate complex. (C)</p> Signup and view all the answers

What is a key characteristic of enzyme inhibition by covalent modification?

<p>It can lead to complete loss of enzyme function. (D)</p> Signup and view all the answers

What is a characteristic feature of competitive inhibitors?

<p>They occupy the active site of the enzyme. (D)</p> Signup and view all the answers

How does competitive inhibition affect Km?

<p>Km increases. (B)</p> Signup and view all the answers

Which compound is an example of a competitive inhibitor that interferes with microbial growth?

<p>Sulphonamides (B)</p> Signup and view all the answers

What does the presence of a competitive inhibitor indicate on a double reciprocal plot?

<p>A shift in the x-intercept. (B)</p> Signup and view all the answers

In the context of competitive inhibition, how does substrate concentration affect the reaction rate?

<p>Increased substrate concentration increases the reaction rate. (D)</p> Signup and view all the answers

What is the EI complex in competitive inhibition?

<p>The complex formed between the inhibitor and enzyme. (D)</p> Signup and view all the answers

Which enzyme is specifically mentioned as being inhibited by malonic acid?

<p>Succinic dehydrogenase (A)</p> Signup and view all the answers

What is the incorrect result of competitive inhibition on enzyme kinetics?

<p>Decreased maximum reaction rate. (B)</p> Signup and view all the answers

What effect does a non-competitive inhibitor have on the Vmax of an enzyme?

<p>Vmax decreases (D)</p> Signup and view all the answers

How does a non-competitive inhibitor alter the shape of the enzyme?

<p>By forming a complex at a site other than the active site (C)</p> Signup and view all the answers

What happens to the Km value when a non-competitive inhibitor is present?

<p>Km remains unaffected (A)</p> Signup and view all the answers

Which of the following statements is true regarding uncompetitive inhibitors?

<p>They bind specifically to the enzyme-substrate complex (B)</p> Signup and view all the answers

What is a key characteristic of non-competitive inhibitors regarding substrate concentration?

<p>Substrate concentration has no effect on inhibitor binding (D)</p> Signup and view all the answers

Which example illustrates non-competitive inhibition?

<p>Cyanide binding to cytochrome oxidase (A)</p> Signup and view all the answers

What type of complexes are formed by non-competitive inhibitors when binding occurs?

<p>Binary and ternary complexes (D)</p> Signup and view all the answers

How does the binding of a non-competitive inhibitor affect the enzyme's efficiency?

<p>Decreases efficiency due to shape change (C)</p> Signup and view all the answers

Flashcards

Vmax

The maximum velocity that an enzyme-catalyzed reaction can reach when the enzyme is fully saturated with substrate.

Km (Michaelis Constant)

The substrate concentration at which the reaction rate is half of its maximum value (Vmax).

Lineweaver-Burk Plot

A graphical representation of the Michaelis-Menten equation, which plots the reciprocal of the initial velocity (1/Vo) against the reciprocal of the substrate concentration (1/[S]).

Initial Velocity (Vo)

The rate of product formation or substrate consumption at a specific substrate concentration.

Signup and view all the flashcards

Michaelis-Menten Equation

The relationship between the initial velocity (Vo) of an enzymatic reaction and the substrate concentration ([S]).

Signup and view all the flashcards

Enzyme Saturation

Saturation state of an enzyme where all active sites are occupied by substrate molecules and the reaction rate is no longer limited by substrate availability.

Signup and view all the flashcards

Enzyme-Substrate Affinity

The binding affinity of an enzyme for its substrate.

Signup and view all the flashcards

Induced Fit

The process of an enzyme changing its shape to fit the substrate molecule more closely.

Signup and view all the flashcards

Enzyme denaturation due to high temperature

The enzyme's shape changes due to the vibrations of its atoms, making the active site unfit for the substrate.

Signup and view all the flashcards

Enzyme denaturation due to pH changes

Changes in pH disrupt the enzyme's shape by altering the charges of acidic and basic groups within the molecule. This affects the active site and leads to denaturation.

Signup and view all the flashcards

Optimal pH for enzyme activity

Each enzyme has a specific pH level where it functions optimally. Moving outside this range decreases activity, and extreme pH can lead to denaturation.

Signup and view all the flashcards

Effect of enzyme concentration on reaction rate

Increasing enzyme concentration directly increases the rate of reaction, as more active sites become available to bind with substrate molecules. This assumes unlimited substrate availability.

Signup and view all the flashcards

Effect of substrate concentration on reaction rate

At low substrate concentrations, reaction rate increases proportionally with substrate concentration. However, at high concentrations, the rate plateaus because all active sites are occupied, and further increase in substrate only adds waiting molecules.

Signup and view all the flashcards

Inhibition of enzyme activity by end products

Some reactions are regulated by end products, which can bind to the enzyme and inhibit its activity. This is a negative feedback mechanism that controls the reaction rate.

Signup and view all the flashcards

Efficiency of enzymes

Enzymes are very efficient catalysts, requiring only low concentrations to achieve a significant reaction rate. Each enzyme molecule can process only one substrate molecule at a time.

Signup and view all the flashcards

Indirect effect of end-product accumulation on reaction rate

The rate of reaction can be indirectly affected by changes in pH caused by the accumulation of end products. This is because pH changes can also affect enzyme activity.

Signup and view all the flashcards

Non-competitive inhibition

A type of enzyme inhibition where the inhibitor binds to a site on the enzyme that is different from the active site, causing a conformational change that affects the enzyme's ability to bind the substrate and/or catalyze the reaction.

Signup and view all the flashcards

Uncompetitive inhibition

A type of enzyme inhibition where the inhibitor binds to an enzyme-substrate complex. This binding inhibits the enzyme's catalytic activity.

Signup and view all the flashcards

Irreversible inhibition

An enzyme inhibitor that binds to an enzyme irreversibly, permanently disabling its catalytic activity.

Signup and view all the flashcards

Vmax decrease

The decrease in the maximum velocity (Vmax) of an enzyme-catalyzed reaction due to inhibition.

Signup and view all the flashcards

Km increase

The increase in the Michaelis constant (Km) due to an inhibitor.

Signup and view all the flashcards

Double Reciprocal Plot

A graphical representation of the Michaelis-Menten equation that plots the reciprocal of the initial velocity (1/Vo) against the reciprocal of the substrate concentration (1/[S]). It helps to analyze enzyme kinetics.

Signup and view all the flashcards

Irreversible Inhibition-Covalent Modification

This type of inhibition resembles the non-competitive inhibition, except that covalent bonds are formed between the inhibitor and the enzyme.

Signup and view all the flashcards

Irreversible Inhibition Plot

In the Michaelis-Menten plot for irreversible inhibition, the curve appears similar to noncompetitive inhibition.

Signup and view all the flashcards

Competitive Inhibitor

A type of inhibitor that structurally resembles the substrate and competes for the active site of the enzyme.

Signup and view all the flashcards

Active Site Inhibition

A type of enzyme inhibition where the inhibitor binds to the enzyme's active site, preventing the substrate from binding.

Signup and view all the flashcards

EI Complex Formation

The formation of a complex between the enzyme and the inhibitor, preventing the enzyme from binding to the substrate.

Signup and view all the flashcards

Inhibition Dependence on Concentrations

The relative concentrations of the inhibitor and substrate determine the effectiveness of the competitive inhibition.

Signup and view all the flashcards

Apparent Km Increase

The apparent increase in Km (Michaelis constant) in the presence of a competitive inhibitor.

Signup and view all the flashcards

Double Reciprocal Plot Shift

The effect of a competitive inhibitor on the double reciprocal plot, which shows a shift in the x-intercept (-1/Km) and the slope (Km/Vmax).

Signup and view all the flashcards

Malonic Acid

An example of a competitive inhibitor that competes with succinate for the active site of succinic dehydrogenase.

Signup and view all the flashcards

How Non-competitive Inhibitors Bind?

This type of inhibitor can bind to both the free enzyme (E) and the enzyme-substrate complex (ES), forming binary (EI) and ternary (ESI) complexes, respectively.

Signup and view all the flashcards

Effect of Non-competitive Inhibitors on Km

A non-competitive inhibitor's binding does not affect the enzyme's affinity for the substrate. This means that the value of Km remains unchanged even in the presence of the inhibitor.

Signup and view all the flashcards

Effect of Non-competitive Inhibitors on Vmax

Non-competitive inhibitors decrease the maximum velocity (Vmax) of the enzyme reaction.

Signup and view all the flashcards

Reversible Inhibitor

A reversible inhibitor can be displaced by the substrate from the binding site on the enzyme.

Signup and view all the flashcards

What are irreversible inhibitors?

Irreversible inhibitors permanently alter the structure of an enzyme by forming a covalent bond with its active site, rendering it inactive.

Signup and view all the flashcards

How does DFP affect acetylcholinesterase?

Diisopropyl fluorophosphate (DFP), a nerve gas, forms a covalent bond with the active site of acetylcholinesterase, an enzyme critical for nerve signal transmission. This inhibition disrupts nerve function, leading to paralysis and potentially death.

Signup and view all the flashcards

How do some insecticides work?

Some insecticides, like parathion, work similarly to DFP by irreversibly inhibiting acetylcholinesterase, leading to insect paralysis and death.

Signup and view all the flashcards

How are enzyme inhibitors used therapeutically?

Many drugs, including antiviral, antibacterial, and antitumor agents, act by inhibiting specific enzymes involved in disease processes. These inhibitors are designed to have limited toxicity to the host.

Signup and view all the flashcards

How does Captopril lower blood pressure?

Captopril, a drug used to manage hypertension, competitively inhibits angiotensin-converting enzyme (ACE). ACE converts angiotensin I to angiotensin II, which raises blood pressure. By blocking ACE, captopril lowers blood pressure.

Signup and view all the flashcards

Study Notes

Mechanism of Enzyme Action

  • Enzymes are typically proteins with a unique shape (conformation).
  • Within the enzyme molecule is an active site with specific properties to bind tightly to the substrate(s).
  • Enzyme-substrate interactions are explained by different theories:
    • Lock and key model: The active site of the enzyme is complementary in shape to the substrate. The substrate fits into the active site like a key into a lock.
    • Induced fit model: The active site changes shape slightly as the substrate binds, fitting tightly to the substrate. This accommodates the transition state.
    • Transition state theory: Enzymes bind to the transition state complex more strongly than to the reactants, accelerating the reaction.

Factors Affecting Enzyme Rate

  • Temperature: Increasing temperature increases kinetic energy, leading to more frequent collisions between enzyme and substrate, and increasing the reaction rate. However, high temperatures denature the enzyme, losing its catalytic activity irreversibly.
  • pH: Changes in pH alter the ionic charge of acidic and basic groups within the enzyme, affecting its shape and active site function. Each enzyme has an optimal pH range for efficient activity; outside this range, enzyme activity decreases. Extremes of pH may denature the enzyme.
  • Enzyme concentration: At low enzyme concentrations the reaction rate increases with enzyme concentration but plateaus eventually at high enzyme concentrations.
  • Substrate concentration: Increasing substrate concentration increases the reaction rate up to the saturation point where all enzyme active sites are occupied. Further increase in substrate concentration does not increase the rate.
  • End-product concentration: Accumulation of end-products can alter the pH of the medium and can inhibit enzyme activity by negative feedback (combining with the enzyme).
  • Inhibition: Inhibitors, small molecules can reduce enzyme activity. Inhibition can be reversible or irreversible.

Types of Inhibition

  • Reversible inhibition: The inhibitor is easily removed from the enzyme, causing no permanent damage.

    • Competitive inhibition: The inhibitor resembles the substrate, competing for the active site of the enzyme. Increasing substrate concentration can overcome competitive inhibition.
    • Non-competitive inhibition: The inhibitor binds to a site other than the active site, changing the enzyme's shape and thus reducing activity. Increasing substrate concentration does not overcome non-competitive inhibition.
    • Uncompetitive inhibition: The inhibitor binds only to the enzyme-substrate complex (ES), preventing the reaction. Both Km and Vmax decrease.

  • Irreversible inhibition: The inhibitor irreversibly binds to the enzyme, permanently altering its shape and thus inactivating the enzyme. Heavy metal ions and certain toxins can cause irreversible inhibition.

Michaelis-Menten Kinetics

  • The Michaelis-Menten model describes the relationship between reaction rate and substrate concentration.
  • It assumes a single substrate, higher substrate concentration than enzyme, and initial velocity is measured.
  • Vmax is the maximum reaction rate possible by an enzyme-catalyzed reaction when the active sites are completely saturated with substrate.
  • Km is the Michaelis constant and signifies the substrate concentration at which the reaction rate is half of Vmax. A low Km indicates high substrate affinity.

Lineweaver-Burk Plot

  • A double reciprocal plot (1/V vs. 1/[S]) of the Michaelis-Menten equation produces a straight line.
  • The slope and y-intercept of this line can be used to determine Km and Vmax, which can help reveal mechanisms of enzyme inhibition.

Therapeutic Applications of Enzyme Inhibitors

  • Several drugs and natural compounds act as enzyme inhibitors to treat various conditions, such as hypertension, hypercholesterolaemia, or cancer.
  • Competitive inhibitors are similar to substrates in structure, which also shows how they can be used to treat diseases. Different types of inhibitors affect different types of enzymes.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Enzyme Action Lecture 4 PDF

Description

Explore the intricate mechanisms of enzyme action, including the guiding theories of enzyme-substrate interactions such as the lock and key model and the induced fit model. Learn how various factors, particularly temperature, affect the rate of enzyme reactions. This quiz covers essential concepts that will deepen your understanding of enzyme functionality in biological systems.

More Like This

Enzyme Kinetics: Understanding Enzyme Reaction Rates and Mechanisms
12 questions

Enzyme Kinetics: Understanding Enzyme Reaction Rates and Mechanisms

TantalizingSequence avatar
TantalizingSequence
Enzyme Kinetics and Inhibition
18 questions

Enzyme Kinetics and Inhibition

MasterfulGrossular avatar
MasterfulGrossular
Enzyme Kinetics and Reaction Mechanisms
40 questions

Enzyme Kinetics and Reaction Mechanisms

LovelyAlgorithm8382 avatar
LovelyAlgorithm8382
Biochemistry Lecture 9: Enzymes
24 questions

Biochemistry Lecture 9: Enzymes

DiplomaticBeryllium avatar
DiplomaticBeryllium
Use Quizgecko on...
Browser
Open
Browser
Browser