Enzymes and Their Functions
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Questions and Answers

What temperature range is considered the optimal temperature for enzyme activity?

  • 25°C to 35°C
  • 30°C to 40°C (correct)
  • 35°C to 45°C
  • 40°C to 50°C

What happens to an enzyme when it is exposed to temperatures between 40°C and 50°C?

  • It becomes more active.
  • It is unaffected.
  • It is permanently inactivated.
  • It undergoes a conformational change. (correct)

What is the effect of a 10°C increase in temperature on the activity of an enzyme, according to the Q10 concept?

  • The activity doubles. (correct)
  • The activity decreases by half.
  • The activity increases by tenfold.
  • The activity remains the same.

What is the ideal storage temperature for substrates and coenzymes?

<p>2°C to 8°C (A)</p> Signup and view all the answers

Which of the following enzymes is classified as a hydrolase?

<p>Acid phosphatase (ACP) (A)</p> Signup and view all the answers

What is the standardized system for classifying and naming enzymes?

<p>Enzyme Commission (EC) system (D)</p> Signup and view all the answers

Which of the following factors can influence the activity of an enzyme?

<p>All of the above (D)</p> Signup and view all the answers

Which of the following enzymes is NOT classified as an oxidoreductase?

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

What happens to the reaction rate when the enzyme concentration increases?

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

When an inhibitor binds to the allosteric site of an enzyme, what type of inhibition is it generally considered?

<p>Non-competitive inhibition (A)</p> Signup and view all the answers

Which of the following is NOT a characteristic of isoenzymes?

<p>Exhibit identical catalytic activity (C)</p> Signup and view all the answers

What effect does a competitive inhibitor have on the Michaelis-Menten constant (Km) of an enzyme?

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

Which one is an example of an inorganic activator that alters the spatial configuration of an enzyme?

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

What is the ES complex in enzyme kinetics?

<p>The complex formed between an enzyme and its substrate (C)</p> Signup and view all the answers

Which of the following statements is true about enzymes?

<p>Enzymes are proteins that speed up chemical reactions. (A)</p> Signup and view all the answers

What is the role of a coenzyme in enzyme kinetics?

<p>To help the substrate fit into the active site of the enzyme (C)</p> Signup and view all the answers

Which of the following enzymes catalyzes the removal of a group from a substrate without hydrolysis?

<p>Glutamate decarboxylase (A)</p> Signup and view all the answers

What type of enzyme specificity does an enzyme exhibit if it combines with all substrates in a particular chemical group?

<p>Group specificity (A)</p> Signup and view all the answers

Which of the following is NOT a general method used in enzyme reaction studies?

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

The 'Induced Fit' theory of enzyme action states that:

<p>The enzyme active site changes shape to accommodate the substrate. (A)</p> Signup and view all the answers

In a zero-order enzyme reaction, the reaction rate is primarily dependent on:

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

What is the standard unit of enzyme activity known as?

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

Which of the following is NOT a factor considered when defining an activity unit for enzymes?

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

Which of the following enzymes is an example of a ligase?

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

Flashcards

Enzyme

A protein that hastens chemical reactions in organic matter.

Active Site

The specific region where substrates bind on an enzyme.

Allosteric Site

A site on the enzyme that binds regulator molecules, affecting activity.

ES Complex

The physical binding of a substrate to the enzyme’s active site.

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Competitive Inhibitor

A molecule that competes with substrate for the active site on an enzyme.

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Non-competitive Inhibitor

A substance that binds to an allosteric site, inhibiting enzyme activity without competing.

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Coenzymes

Organic compounds that assist enzymes by helping substrates to fit.

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Isoenzymes

Enzymes with different molecular structures but catalyze the same reaction.

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Temperature Effect on Enzymes

Higher temperature increases the activity of chemical reactions and enzymes up to a certain point, after which enzymes can denature.

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Temperature Coefficient (Q10)

For every 10°C increase in temperature, enzyme activity can double.

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Optimal pH for Reactions

Physiological reactions typically occur optimally at pH levels between 7 and 8.

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Effect of Extreme pH

Extreme pH levels can denature enzymes, alter ionic states, cause structural changes, and change the charge of amino acids.

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Enzyme Storage Temperature

Low temperatures (like refrigeration) can keep enzymes reversibly inactive, while too much freezing can cause denaturation.

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Enzyme Nomenclature

Enzymes are named and classified by the Enzyme Commission based on function, substrate catalyzed, and class of reaction.

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Enzyme Classification: Oxidoreductases

Enzymes that catalyze the removal or addition of electrons in oxidation-reduction (redox) reactions.

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Enzyme Example: Alkaline Phosphatase (ALP)

A specific enzyme classified as a hydrolase that catalyzes the removal of phosphate groups from various compounds.

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Lyases

Enzymes that catalyze the removal of groups without hydrolysis.

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Isomerases

Enzymes that catalyze intramolecular rearrangements of substrates.

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Ligase

Enzymes that join two substrates while breaking a pyrophosphate bond.

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Lock and Key Theory

Model suggesting substrate fits enzyme's active site like a key into a lock.

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Induced Fit Theory

Model where enzyme changes shape to accommodate the substrate upon binding.

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Absolute Specificity

Enzymes that catalyze only one reaction with a specific substrate.

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Enzyme Kinetics

Study of how enzyme reactions depend on substrate concentration and energy.

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International Unit (IU)

Measurement indicating 1 micromole of substrate processed per minute.

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Study Notes

Enzymes

  • Enzymes hasten chemical reactions in organic matter
  • Catalyze specific chemical reactions
  • Found in large quantities within cells
  • Increase membrane permeability, allowing them to enter the bloodstream
  • Measured by activity, not absolute value
  • Appear in serum after cell injury, degradation, or storage
  • Specific to a substrate, converting it to a defined product
  • Used clinically as a sign of organ damage

Enzyme Components

  • Active site: Water-free cavity where substrate interacts
  • Allosteric site: Cavity other than the active site, binding regulator molecules

ES Complex

  • Physical binding of a substrate to the enzyme's active site

Factors Affecting Enzymatic Reactions

  • Enzyme Concentration: Higher concentration results in faster reaction rate within the substrate range
  • Substrate Concentration: Reaction rate increases with substrate up to saturation. Further increases have no effect
  • Cofactors:
    • Coenzymes: Organic molecules aiding substrate fit. Increased coenzymes increase reaction velocity. Examples include NAD and NADP
    • Activators: Inorganic ions altering enzyme shape for proper binding. Examples include calcium, zinc, chloride, magnesium, and potassium.
    • Metalloenzymes: Inorganic ions attached to the enzyme. Examples include catalase and cytochrome oxidase.

Inhibitors

  • Competitive Inhibitors: Bind to the active site, competing with the substrate. Reversible if substrate surpasses inhibitor concentration
  • Noncompetitive Inhibitors: Do not compete with the substrate (bind to an allosteric site), causing irreversible inhibition.
  • Uncompetitive Inhibitors: Bind to the enzyme-substrate complex (ES), increasing inhibition with increased substrate

Isoenzymes

  • Enzymes with identical, catalytic reactions yet varying structures and amino acid sequences

Temperature

  • Optimal temperature is 25-37 degrees Celsius
  • Denaturation occurs above 40 degrees Celsius
  • Inactivation above 60-65 degrees Celsius
  • Temperature coefficient (Q10): a 10-degree increase in temperature leads to roughly a twofold increase in enzyme activity

pH

  • Physiological range is 7-8
  • Extreme pH denatures enzymes and alters charge in the amino acid residues within the active site

Storage

  • Low temperatures (refrigeration/freezing) result in reversible inactivity.
  • Repeated freezing/thawing denatures proteins
  • -20 degrees Celsius is best for long-term storage
  • 2-8 degrees Celsius is suitable for substrate and coenzyme storage
  • Room temperature is good for LD4 and LD5 storage

Hemolysis

  • Increased enzyme concentration due to erythrocyte rupture

Lactescence/Milky Specimen

  • Increased enzyme concentration

Enzyme Nomenclature

  • Standardized by the Enzyme Commission (EC) using a classification system
  • Classified by biochemical function, substrate catalyzed, class of reaction.
  • Individual identification numbers (AMS EC 3.2.1.1)

Other factors

  • Hemolysis and lactescence can cause elevated enzyme concentration
  • Enzyme theory includes lock-and-key and induced-fit models
  • Enzyme kinetics deals with rate of reactions and affects of factors like substrate and enzyme concentrations, temperature, etc

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Enzymes Introduction Notes PDF

Description

Explore the fascinating world of enzymes and their critical role in biological reactions. This quiz delves into enzyme components, the ES complex, and factors influencing enzymatic reactions. Enhance your understanding of how enzymes operate within living cells and their clinical significance.

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