Human Body Function 102: Enzymes Quiz
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Questions and Answers

Enzymes function by ____________ the activation energy needed for reactions.

  • Inhibiting
  • Decreasing (correct)
  • Neutralizing
  • Increasing

Which of the following classifications accurately represents enzymes?

  • Enzymes are lipids
  • Enzymes are proteins (correct)
  • Enzymes are carbohydrates
  • Enzymes are nucleic acids

What is the usual optimum pH range for most enzymes to function effectively?

  • Between 3 and 5
  • Between 6 and 8
  • Above 10
  • Between 5 and 9 (correct)

Which of the following factors does NOT influence the rate of enzyme-catalyzed reactions?

<p>Color of the enzyme (A)</p> Signup and view all the answers

Enzymes are classified into how many major classes?

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

Which class of enzymes is responsible for catalyzing oxidation-reduction reactions?

<p>Oxido-reductases (D)</p> Signup and view all the answers

What type of enzyme catalyzes the addition of water to cleave bonds?

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

Which enzyme class is NOT involved in the rearrangement of molecular structures?

<p>Ligases (C)</p> Signup and view all the answers

Which of the following enzyme classifications centers on the transfer of functional groups?

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

Which enzyme class is characterized by catalyzing bond breakage without the addition of water?

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

Enzymes used as therapeutic agents can be best classified under which category?

<p>Oxido-reductases (B)</p> Signup and view all the answers

What is the primary function of ligases in enzymatic reactions?

<p>To join two large molecules by forming new bonds (B)</p> Signup and view all the answers

What is a key characteristic of isomerases?

<p>They catalyze structural rearrangements in molecules. (C)</p> Signup and view all the answers

Which of the following correctly identifies a diagnostic use of enzymes?

<p>Enzymes as diagnostic markers for diseases (B)</p> Signup and view all the answers

Which type of reaction would hydrolases NOT be involved in?

<p>Dehydration to form a polymer (B)</p> Signup and view all the answers

What does a smaller Km indicate about the enzyme's affinity for its substrate?

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

How does increasing cofactor concentration affect the velocity of a reaction?

<p>It increases the velocity directly proportional to cofactor concentration (A), It increases the velocity up to a certain saturation point (D)</p> Signup and view all the answers

What is the effect of inhibitor concentration on the velocity of an enzyme-catalyzed reaction?

<p>Inversely proportional decrease (D)</p> Signup and view all the answers

What happens to enzyme activity as temperature increases beyond the optimum level?

<p>Enzyme becomes denatured (C)</p> Signup and view all the answers

What is the most favorable pH range for most enzymes?

<p>5 to 9 (B)</p> Signup and view all the answers

How does the passage of time generally affect the velocity of an enzyme-catalyzed reaction?

<p>Velocity decreases as products form (B)</p> Signup and view all the answers

What is the optimum temperature for enzyme activity?

<p>37°C (D)</p> Signup and view all the answers

If the pH moves 2 units away from an enzyme's optimum pH, what is likely to happen?

<p>Enzyme activity stops completely (C)</p> Signup and view all the answers

What indicates a higher Km value for an enzyme?

<p>Lower affinity for substrate (C)</p> Signup and view all the answers

At which point does increasing enzyme concentration not further increase reaction velocity?

<p>At substrate saturation (B)</p> Signup and view all the answers

What is the mechanism of enzyme action described by the induced fit model?

<p>The substrate binds and the enzyme changes shape for an ideal fit. (A)</p> Signup and view all the answers

Which factor does NOT affect the rate of enzyme-catalyzed reactions?

<p>Size of the substrate molecule (B)</p> Signup and view all the answers

What does the Michaelis constant (Km) indicate about an enzyme's interaction with its substrate?

<p>The substrate concentration that generates half of Vmax. (A)</p> Signup and view all the answers

How does increasing substrate concentration affect an enzyme-catalyzed reaction?

<p>It has no effect once the enzyme is saturated. (A)</p> Signup and view all the answers

Which of the following accurately describes an inhibitor in enzyme reactions?

<p>They decrease the rate of enzyme activity. (B)</p> Signup and view all the answers

What occurs when an enzyme is said to be in a saturated state?

<p>Substrate is converting to product at maximum rate. (B)</p> Signup and view all the answers

Which of the following factors would most likely lead to an increase in enzyme velocity, assuming other conditions are optimal?

<p>Higher temperature which is not beyond the enzyme's stability. (B)</p> Signup and view all the answers

What relationship does the initial velocity (Vi) have with substrate concentration [S] before reaching maximum velocity (Vmax)?

<p>Vi increases in direct proportion to [S] until saturation is reached. (D)</p> Signup and view all the answers

In enzyme kinetics, which scenario illustrates a high affinity between an enzyme and its substrate?

<p>A low Km value. (D)</p> Signup and view all the answers

What is the primary role of cofactors in enzyme catalysis?

<p>To enhance the enzymatic activity. (C)</p> Signup and view all the answers

What is the primary role of enzymes in biochemical reactions?

<p>They act as biocatalysts to regulate reaction rates. (B)</p> Signup and view all the answers

Which of the following statements about substrates is correct?

<p>Each enzyme is specific to a particular substrate. (C)</p> Signup and view all the answers

What term describes the active site of an enzyme?

<p>Catalytic site (A)</p> Signup and view all the answers

Which of the following is NOT a characteristic of enzymes?

<p>They can function in extremely large amounts. (D)</p> Signup and view all the answers

What is the term for a conjugated enzyme?

<p>Holoenzyme (C)</p> Signup and view all the answers

What are cofactors in the context of enzymes?

<p>They are required non-protein molecules aiding enzyme activity. (B)</p> Signup and view all the answers

Which factor does NOT typically affect enzyme activity?

<p>Color of the enzyme (C)</p> Signup and view all the answers

How do enzymes affect the velocity of biochemical reactions?

<p>They accelerate the reaction rate without changing the equilibrium. (D)</p> Signup and view all the answers

Flashcards

Enzymes

Biological catalysts that speed up biochemical reactions without being consumed in the process.

Substrate

The molecule that an enzyme acts upon.

Products

The molecules produced by an enzyme-catalyzed reaction.

Active site

The specific region on an enzyme where the substrate binds.

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Holoenzyme

The complete functional enzyme, consisting of an apoenzyme and a cofactor.

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Apoenzyme

The protein component of an enzyme.

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Cofactor

A non-protein molecule that helps an enzyme function.

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Production and Action of Enzymes

Enzymes are produced by living cells and can function both inside and outside these cells.

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Induced-fit model

The model where the enzyme's active site changes slightly when a substrate binds, allowing for perfect fit and catalysis.

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Activation Energy

Energy needed for a reaction to occur, enzymes lower this energy, increasing reaction rate.

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Michaelis Constant (Km)

A measure of the substrate concentration required to reach half the maximum reaction velocity (Vmax).

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Maximum Velocity (Vmax)

The maximum rate at which an enzyme can catalyze a reaction, achieved at high substrate concentrations.

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Michaelis-Menten Curve

The relationship between substrate concentration and initial reaction velocity, usually illustrated as a curve.

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Substrate Concentration Effect

The rate of an enzyme-catalyzed reaction increases directly with the concentration of the enzyme-substrate complex.

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Enzyme Saturation

The enzyme's 'active site' becomes saturated with substrate, meaning further increases in substrate concentration no longer increase the reaction rate.

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Enzyme Concentration Effect

Increasing the enzyme concentration directly increases the reaction rate by providing more active sites.

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Inhibitors

Molecules that slow or block enzyme activity, often mimicking the substrate to bind to the active site.

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What do enzymes do?

Enzymes are biological catalysts that accelerate chemical reactions by lowering the activation energy required for those reactions.

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What does an enzyme work on?

The specific molecule that an enzyme acts upon is known as the substrate.

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What is the optimal pH for most enzymes?

The optimal pH for most enzymes falls within a range between 5 and 9.

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What are enzymes made of?

Enzymes are protein molecules that act as biological catalysts, speeding up biochemical reactions without being consumed in the process.

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How are enzymes classified?

Enzymes are classified into six major categories based on the type of reaction they catalyze.

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What are enzymes?

Enzymes are biological catalysts that speed up biochemical reactions without being consumed in the process.

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What do oxidoreductases do?

Oxido-reductases catalyze oxidation-reduction reactions, where electrons are transferred between molecules.

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What do transferases do?

Transferases move specific functional groups from one molecule to another.

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What do hydrolases do?

Hydrolases break down molecules by adding water, causing bonds to split.

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What do lyases do?

Lyases break chemical bonds without adding water, often creating double bonds.

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What do isomerases do?

Isomerases rearrange the atoms within a molecule to create different isomers.

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What do ligases do?

Ligases join two large molecules together using energy, forming a new chemical bond.

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How can enzymes be used in diagnosis?

Enzymes can be used as diagnostic markers to detect specific diseases in the body.

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How can enzymes be used therapeutically?

Enzymes can serve as therapeutic agents, directly treating certain medical conditions.

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What is the Michaelis constant (Km) in enzyme kinetics?

The Michaelis constant (Km) represents the substrate concentration at which an enzyme achieves half of its maximum velocity (Vmax). A lower Km indicates that the enzyme has a higher affinity for its substrate, requiring a lower substrate concentration to reach half-maximal velocity.

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What is Vmax in enzyme kinetics?

The maximum rate of an enzymatic reaction is known as Vmax. It represents the rate at which the enzyme is saturated with substrate and working at its full potential.

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How does increasing enzyme concentration affect reaction velocity?

Increasing enzyme concentration directly increases the reaction velocity, leading to a higher rate of product formation. This is because more enzyme molecules are available to bind to and convert substrate into product.

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How do cofactors influence enzyme activity?

Cofactors are non-protein molecules that assist enzymes in carrying out their catalytic functions. They can be metal ions or organic molecules. Increasing cofactor concentration generally increases the reaction velocity, as more cofactors are available to aid the enzyme.

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What effect do inhibitors have on enzyme activity?

Inhibitors are molecules that reduce or block the activity of enzymes by binding to the enzyme and interfering with its ability to bind substrate or catalyze the reaction. Increasing inhibitor concentration decreases reaction velocity as more inhibitors are available to block the enzyme.

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How does temperature affect enzyme activity?

Higher temperatures generally increase the rate of enzyme-catalyzed reactions up to a certain point. This is because increased kinetic energy leads to more collisions between the enzyme and substrate. However, excessive heat can denature the enzyme, causing it to lose its active conformation and function.

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How does pH affect enzyme activity?

Most enzymes have an optimal pH at which they function maximally. Deviation from this optimal pH can disrupt the enzyme's structure and activity, leading to a decrease in reaction velocity. The optimum pH tends to be slightly alkaline, typically between 5 and 9, but can vary depending on the specific enzyme and its cellular environment.

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Why does reaction velocity decrease over time?

As a reaction proceeds, the supply of substrate decreases and the product concentration increases, leading to a decrease in reaction velocity. Additionally, enzymes can become deactivated over time, contributing to the decline in reaction velocity.

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What is the active site of an enzyme?

The active site is a specific region on an enzyme molecule that is responsible for binding to the substrate and catalyzing the reaction. It has a unique three-dimensional shape and amino acid composition that complements the shape of the substrate molecule, ensuring specific interactions.

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Study Notes

Course Information

  • Academic Year: 2024-2025
  • Year: 1
  • Semester: 1
  • Module: Human Body Function (HBF) 102

Enzymes

  • Enzymes are biocatalysts that regulate the speed of biochemical reactions.
  • Substrates are the molecules acted upon by enzymes. Enzymes are specific to their substrates.
  • Products are formed during the reaction, aided by the enzyme.
  • Active site is the region of an enzyme where a substrate molecule binds, also called the catalytic site or substrate-binding site.
  • An enzyme's active site has a specific shape that allows it to bind to a specific substrate molecule.

Enzyme Objectives

  • Define enzymes and understand their significance in medicine.
  • Categorize enzymes into six main groups.
  • Identify the general characteristics of enzymes.
  • Explain the mechanism of enzyme actions.
  • Describe factors that impact enzyme activity and reaction rate.
  • Enzyme activity is optimal at 37°C.
  • Enzymes are proteins.

Enzyme Common Features

  • Enzymes are made by living cells and can operate outside cells.
  • They're effective in small quantities.
  • They speed up reactions without affecting equilibrium.
  • Enzymes aren't chemically modified after the reaction finishes.
  • They have varying degrees of substrate specificity (specific substrates or related ones).

Chemical Nature of Enzymes

  • Most enzymes are proteins, either simple or conjugated.
  • Holoenzyme: The conjugated protein.
  • Apoenzyme: The protein component.
  • Cofactor: The non-protein component assists the reaction.

Enzyme Mechanism (Induced Fit Model)

  • A substrate attaches to the active site.
  • The active site's shape slightly changes to fit the substrate better.
  • An ideal fit is generated for catalysis.
  • Enzymes decrease the activation energy, required for a reaction to occur.

Factors Affecting Enzyme Activity

  • Substrate concentration ([S]) — Directly proportional to the enzyme-substrate complex concentration, up to saturation.
  • Enzyme concentration (E) — Reaction velocity increases with enzyme concentration; plateaus when maximum reached.
  • Cofactor concentration (C) — Reaction velocity increases proportionally with cofactor concentration, up to a point.
  • Inhibitor concentration (I) — Inversely proportional to reaction velocity.
  • Temperature — Enzyme-catalyzed reaction rate increases with rising temperature up to an optimal temperature of 37°C. Above this, denaturation can occur.
  • pH — Enzymes function best at a specific pH; activity decreases significantly above or below this optimal range (typically within 5-9).
  • Time — Enzyme activity diminishes as substrates are consumed, and enzymes become inactive over time.

Enzyme Classification

  • Enzymes are categorized into six classes based on the reaction type they catalyze:
    • Oxidoreductases
    • Transferases
    • Hydrolases
    • Lyases
    • Isomerases
    • Ligases

Biomedical Importance of Enzymes

  • Diagnostic markers for tissue-specific diseases.
  • Commercial diagnostic reagents for biochemical tests.
  • Therapeutic agents.
  • Drug targets.

Interactive Questions

  • Definition of enzyme.
  • List 3 factors affecting enzyme activity.
  • Explain why enzyme activity stops at 70°C.
  • How do enzymes speed up reactions?
  • What is an enzyme made of?
  • What is the optimum pH for most enzymes?

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Lecture 9 Enzymes-1 PDF

Description

Test your knowledge on enzymes in the Human Body Function module. This quiz covers the definitions, classifications, mechanisms of action, and factors affecting enzyme activity. Dive into the crucial role enzymes play in biochemistry and medicine.

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