Enzymes: Structure, Function, and Regulation for Biology Year 13

Question 1

Where within an enzyme does the enzyme-substrate complex form?

Accepted Answer

Active site

Answer

Allosteric site

Answer

Coenzyme binding site

Answer

Binding site for competitive inhibitors

Question 2

Which factor does NOT directly affect enzyme activity?

Accepted Answer

Molecular weight

Answer

Temperature

Answer

pH

Answer

Substrate concentration

Question 3

Which factor has no direct impact on the rate of an enzyme-catalyzed reaction?

Accepted Answer

Magnetic field strength

Answer

Enzyme concentration

Answer

Substrate concentration

Answer

Temperature

Question 4

Which molecules control the activity of allosteric enzymes by binding to specific sites and causing a conformational change?

Accepted Answer

Effector molecules

Answer

Coenzymes

Answer

Prosthetic groups

Answer

pH

Question 5

Which enzyme component is crucial for enzyme catalysis and is chemically separate from the enzyme's amino acid sequence?

Accepted Answer

A. Cofactor

Answer

B. Prosthetic group

Answer

C. Active site

Answer

D. Apoenzyme

Question 6

Which of the following statements accurately describes competitive enzyme inhibition?

Accepted Answer

Competitive inhibitors bind to the enzyme's active site, blocking substrate binding and decreasing enzyme activity.

Answer

Competitive inhibitors bind to an allosteric site, causing a conformational change that affects enzyme activity.

Answer

Competitive inhibitors bind to the substrate-enzyme complex, increasing the Km and decreasing the Vmax.

Answer

Competitive inhibitors form covalent bonds with the enzyme, permanently deactivating it.

Question 7

What is the optimal pH range for most human enzymes?

Accepted Answer

6.5-7.5

Answer

1.0-2.0

Answer

4.0-5.0

Answer

9.0-10.0

Question 8

Which factor does **NOT** directly affect an enzyme's catalytic efficiency?

Accepted Answer

Presence of non-competitive inhibitors

Answer

Temperature

Answer

pH

Answer

Enzyme concentration

Question 9

Which factor does NOT directly affect an enzyme's catalytic activity?

Accepted Answer

Product concentration

Answer

Temperature

Answer

pH

Answer

Enzyme concentration

Question 10

In competitive enzyme inhibition, the inhibitor:

Accepted Answer

Binds to the active site of the enzyme, competing with the substrate

Answer

Binds to the enzyme-substrate complex

Answer

Binds to an allosteric site on the enzyme, altering its conformation

Answer

Is converted into the product by the enzyme

Question 11

Which factor does NOT directly influence the rate of an enzyme-catalyzed reaction?

Accepted Answer

Amount of product

Answer

Temperature

Answer

pH

Answer

Substrate concentration

Question 12

Which of the following statements about enzymes is not entirely accurate?

Accepted Answer

Enzymes can shift the equilibrium position of a reaction.

Answer

Enzymes increase the rate of chemical reactions they catalyze.

Answer

Enzymes are highly specific, meaning they exclusively catalyze a particular type of reaction or a narrow range of related reactions.

Answer

Enzymes can be affected by environmental factors such as pH and temperature, potentially losing their catalytic activity under extreme conditions.

Question 13

In enzyme-catalyzed reactions, what is the primary function of enzymes?

Accepted Answer

Stabilizing the high-energy transition state of substrates

Answer

Forming permanent covalent bonds with substrates

Answer

Increasing substrate concentration in the reaction mixture

Answer

Being consumed and used up during the reaction

Question 14

Which of the following is a key characteristic of enzymes?

Accepted Answer

Enzymes are very specific for their substrates.

Answer

Enzymes are used up in the reactions they catalyze.

Question 15

How does a competitive enzyme inhibitor function?

Accepted Answer

Binds reversibly to the enzyme's active site, competing with the substrate for binding.

Answer

Binds irreversibly to the enzyme's active site, causing permanent inhibition.

Answer

Binds allosterically to the enzyme, causing a conformational change that reduces its catalytic activity.

Answer

Forms a covalent bond with an amino acid residue essential for enzyme catalysis, causing irreversible inhibition.

Question 16

As the substrate concentration of an enzyme-catalyzed reaction increases, the reaction rate will continue to increase until what point is reached?

Accepted Answer

All active sites on the enzyme molecules are occupied

Answer

The substrate concentration reaches the Michaelis constant

Answer

The enzyme concentration becomes equal to the substrate concentration

Answer

The temperature reaches the optimum temperature for the enzyme

Question 17

Which type of biochemical molecule is the primary component of enzymes?

Accepted Answer

Proteins

Answer

Carbohydrates

Answer

Lipids

Answer

Nucleic acids

Question 18

Enzymes are classified based on the reactions they catalyze. Outline the six main enzyme classes, providing specific examples of enzymes and their corresponding reactions.

Accepted Answer

Oxidoreductases catalyze oxidation-reduction reactions, exemplified by dehydrogenases, which facilitate the removal of hydrogen atoms.

Accepted Answer

Transferases catalyze the transfer of functional groups, such as kinases, which add phosphate groups to molecules.

Accepted Answer

Hydrolases catalyze hydrolysis reactions, exemplified by esterases, which break ester bonds.

Accepted Answer

Lyases catalyze the cleavage of various bonds without hydrolysis, such as decarboxylases, which remove carboxyl groups.

Question 19

In enzyme kinetics, the Michaelis-Menten equation helps us understand how enzymes interact with substrates. What does the Michaelis constant (K_m) represent in this equation?

Accepted Answer

K_m is the substrate concentration when the enzyme reaches half its maximum speed.

Answer

K_m is the maximum speed of an enzyme-catalyzed reaction.

Answer

K_m is the substrate concentration when the enzyme is fully saturated.

Answer

K_m is a constant that does not depend on the enzyme concentration.

Question 20

Which action is characteristic of a competitive enzyme inhibitor?

Accepted Answer

Binds to the enzyme's active site, blocking substrate access.

Answer

Binds to a different site, altering enzyme shape and reducing activity.

Answer

Enhances enzyme-substrate binding affinity.

Answer

Irreversibly deactivates the enzyme.

Question 21

How does enzyme activity typically change as substrate concentration increases?

Accepted Answer

Enzyme activity reaches a maximum velocity and then plateaus.

Answer

Enzyme activity increases linearly.

Answer

Enzyme activity increases exponentially.

Question 22

Which experimental technique is primarily used to determine the 3D structure of enzymes?

Accepted Answer

X-ray crystallography

Answer

Electrophoresis

Answer

Spectrophotometry

Question 23

When designing an enzyme for industrial use, which factor is NOT a primary consideration?

Accepted Answer

Enzyme production cost

Answer

Substrate specificity

Answer

pH and temperature stability

Answer

Cofactor requirements

Question 24

Enzyme immobilization offers several advantages. Which of the following is NOT a benefit of enzyme immobilization?

Accepted Answer

Diminished enzyme activity

Answer

Enhanced enzyme stability

Answer

Simplified product retrieval

Answer

Elevated specificity

Question 25

How does temperature affect enzyme activity? Describe the optimal temperature range for enzyme function.

Accepted Answer

Enzyme activity increases steadily with rising temperature, peaks at the optimal temperature, then drops abruptly due to enzyme denaturation.

Answer

Enzyme activity decreases steadily with rising temperature, reaches a low point at the optimal temperature, then rises sharply.

Answer

Enzyme activity stays the same regardless of temperature changes.

Answer

Enzyme activity increases exponentially with rising temperature, peaks at the optimal temperature, then decreases exponentially.

Question 26

Evaluate the ethical and environmental implications of enzyme use in industry. Consider both the potential risks and benefits of enzyme technology and its impact on sustainable development.

Accepted Answer

Careful consideration of the ethical and environmental implications is crucial for the responsible and sustainable use of enzyme technology.

Answer

Enzyme technology poses no ethical or environmental concerns due to its natural and biodegradable nature.

Answer

Enzyme use in industry is risk-free for human health and the environment because enzymes are highly specific.

Answer

Enzyme technology solely offers benefits by reducing the need for harsh chemicals and energy consumption.

Question 27

Which adjustments can optimize enzyme activity for industrial applications?

Accepted Answer

Maintain optimal temperature and pH, increase substrate concentration, and immobilize enzymes.

Answer

Raise temperature and pH, while lowering substrate and enzyme concentrations.

Answer

Lower temperature, raise pH, and employ enzyme inhibitors.

Question 28

Select the enzyme that hydrolyzes proteins:

Accepted Answer

Pepsin

Answer

Amylase

Answer

Lipase

Answer

Sucrase

Question 29

The Michaelis constant (Km) indicates:

Accepted Answer

Substrate concentration at half-maximal reaction rate

Answer

Maximum reaction velocity

Answer

Enzyme's affinity for the substrate

Answer

Enzyme's turnover rate

Question 30

Describe the mechanism by which the enzyme-substrate complex is formed.

Accepted Answer

Combination of induced fit and lock-and-key.

Answer

Induced fit: Enzyme shape changes to accommodate substrate.

Answer

Lock-and-key: Substrate fits perfectly into a rigid enzyme active site.

Answer

Neither induced fit nor lock-and-key.

Question 31

Which substance is an example of a coenzyme?

Accepted Answer

Nicotinamide adenine dinucleotide (NAD+)

Answer

Heme

Answer

Adenosine triphosphate (ATP)

Answer

An amino acid

Question 32

Describe competitive enzyme inhibition.

Accepted Answer

Inhibitor binds to the active site, competing with the substrate.

Answer

Inhibitor binds elsewhere, altering enzyme shape.

Answer

Inhibitor binds to the substrate, hindering its binding to the enzyme.

Answer

Inhibitor binds to the enzyme-substrate complex, preventing the reaction.

Question 33

Which step in an enzyme-catalyzed reaction is known as the rate-limiting step?

Accepted Answer

Step with the slowest reaction rate.

Answer

Step with the highest activation energy.

Answer

Step with the lowest activation energy.

Answer

Step with the highest substrate concentration.

Question 34

Which of the following is a characteristic of enzymes?

Accepted Answer

They are highly specific for their substrates.

Answer

They increase the activation energy of reactions.

Answer

They can be used up in the reactions they catalyze.

Answer

They are lipids.

Question 35

Which type of bond is primarily involved in the formation of the enzyme-substrate complex?

Accepted Answer

Hydrogen bond

Answer

Covalent bond

Answer

Ionic bond

Answer

Van der Waals forces

Question 36

The Michaelis-Menten constant (K_m) represents:

Accepted Answer

The substrate concentration at which the enzyme is half-saturated.

Answer

The maximum rate of the enzyme-catalyzed reaction.

Answer

The affinity of the enzyme for its substrate.

Answer

The specificity of the enzyme for its substrate.

Question 37

The primary role of cofactors in enzyme catalysis is to:

Accepted Answer

Provide electrons or protons for the reaction.

Answer

Provide the active site with the correct shape.

Answer

Lower the activation energy of the reaction.

Answer

Bind to the substrate and bring it closer to the enzyme.

Question 38

Explain how immobilizing enzymes on matrices enhances their stability and discuss the advantages of this technique in industrial applications.

Accepted Answer

Enzyme immobilization protects enzymes from denaturation, preserving their activity over longer periods.

Accepted Answer

Enzyme immobilization facilitates the separation of enzymes from the reaction mixture, allowing for easy recovery and reuse.

Answer

Enzyme immobilization significantly increases the reaction rate of enzymes.

Answer

Enzyme immobilization is exclusively applicable to enzymes with high molecular weights.

Question 39

Which experimental technique provides insights into enzyme conformational changes occurring on a millisecond timescale?

Accepted Answer

Stopped-flow spectroscopy

Answer

Circular dichroism (CD) spectroscopy

Answer

Cryo-electron microscopy (Cryo-EM)

Answer

Isothermal titration calorimetry (ITC)

Question 40

Describe how enzyme immobilization techniques enhance enzyme stability and reusability in industrial applications. Provide specific examples of enzyme immobilization methods and their benefits.

Accepted Answer

Enzyme immobilization increases enzyme stability by preventing denaturation and proteolysis.

Accepted Answer

Enzyme immobilization allows for easy enzyme recovery and reuse, reducing production costs.

Answer

Enzyme immobilization does not improve enzyme activity or substrate specificity.

Question 41

Explain how enzymes catalyze chemical reactions. Describe the mechanism by which they lower the activation energy and identify the factors that affect their catalytic efficiency.

Accepted Answer

Enzymes provide an alternative reaction pathway, reducing the activation energy and increasing the reaction rate.

Answer

Enzymes directly modify the structure of substrates, enhancing their reactivity.

Answer

Enzymes lower reactant concentrations, speeding up the reaction.

Answer

Enzymes utilize energy to push reactions forward.

Question 42

How does allosteric regulation help control metabolism in cells?

Accepted Answer

It adjusts metabolic pathways by changing enzyme activity based on cell conditions.

Answer

It enhances enzyme specificity for substrates.

Answer

It prevents enzyme inhibition by blocking inhibitor binding.

Question 43

Which experimental techniques are used to determine the three-dimensional structure of enzymes?

Accepted Answer

X-ray crystallography

Accepted Answer

Nuclear magnetic resonance (NMR) spectroscopy

Accepted Answer

Cryo-electron microscopy (cryo-EM)

Answer

Mass spectrometry

Question 44

Define enzyme inhibition and outline two specific examples of how enzyme inhibitors are utilized in medical treatments.

Accepted Answer

Enzyme inhibitors impede enzyme activity by binding to the active site, hindering substrate binding and catalysis.

Answer

Enzyme inhibitors enhance the rate of enzyme reactions.

Answer

Enzyme inhibitors have no medical applications.

Question 45

The active site of an enzyme is:

Accepted Answer

A specific region of the enzyme that binds and modifies the substrate.

Answer

The entire surface of the enzyme where the reaction takes place.

Answer

A group of amino acids that are responsible for catalysis.

Answer

A site where the enzyme is synthesized.

Question 46

Competitive inhibition occurs when:

Accepted Answer

A molecule binds to the active site of the enzyme, competing with the substrate for binding.

Answer

A molecule binds to an allosteric site on the enzyme, altering its shape and activity.

Answer

The substrate concentration is too low or too high.

Answer

The temperature is too high or too low.

Question 47

Which of the following enzymes is responsible for breaking down hydrogen peroxide in red blood cells?

Accepted Answer

Catalase

Answer

Peroxidase

Answer

Superoxide dismutase

Answer

Glutathione reductase

Question 48

The Michaelis-Menten constant (Km) of an enzyme is defined as:

Accepted Answer

The substrate concentration at which the enzyme is half-saturated and operating at half of its maximum velocity.

Answer

The maximum velocity of the enzyme-catalyzed reaction.

Answer

The equilibrium constant for the enzyme-substrate complex formation.

Answer

The rate constant for the enzyme-catalyzed reaction.

Question 49

Which of the following is a cofactor for many enzymes?

Accepted Answer

NAD+

Answer

ATP

Answer

Hemoglobin

Answer

Amino acids

Question 50

Which of the following is NOT an application of enzymes in biotechnology?

Accepted Answer

Energy storage

Answer

Production of biofuels

Answer

Synthesis of pharmaceuticals

Answer

Wastewater treatment

Question 51

Enzymes are essential for life because they:

Accepted Answer

Control the rate and regulation of biochemical reactions.

Answer

Provide energy for cells.

Answer

Transport molecules across cell membranes.

Answer

Store genetic information.

Question 52

How does natural selection contribute to the variation and specificity of enzymes in different organisms?

Accepted Answer

Natural selection favors enzymes with higher specificity for their substrates, enhancing catalytic efficiency and optimizing cellular processes.

Answer

Natural selection primarily targets enzymes involved in energy metabolism, as these are essential for survival.

Answer

Enzyme evolution occurs randomly, and natural selection has no influence on their diversity and specificity.

Answer

Genetic mutations solely account for enzyme diversity, with natural selection playing a minor role.

Question 53

How do changes in temperature and pH affect enzyme activity?

Accepted Answer

Temperature and pH affect both enzyme structure and function.

Answer

Temperature and pH have no effect on enzyme activity.

Answer

Temperature and pH only affect enzyme structure.

Answer

Temperature and pH only affect enzyme function.

Question 54

Enzymes exhibit remarkable specificity for their substrates. This characteristic means that:

Accepted Answer

An enzyme will catalyze a reaction only with a specific substrate or a narrow range of structurally similar substrates.

Answer

Enzymes can bind to multiple substrates simultaneously.

Answer

Enzymes are not affected by the chemical structure of their substrates.

Answer

Enzymes can catalyze any type of chemical reaction.

Question 55

The active site of an enzyme:

Accepted Answer

Is a specific region of the enzyme that binds the substrate and facilitates the chemical reaction.

Answer

Is a random region of the enzyme that changes shape to accommodate different substrates.

Answer

Is the entire surface of the enzyme.

Question 56

Researchers use various techniques to study the intricate structure of enzymes. Which of the following techniques is commonly employed for this purpose?

Accepted Answer

X-ray crystallography.

Answer

Mass spectrometry.

Answer

Gel electrophoresis.

Answer

Chromatography.

Question 57

Which of the following **factors** can **affect enzyme activity**?

Accepted Answer

Temperature, pH, substrate concentration, and enzyme concentration.

Answer

Sound waves and humidity.

Answer

Light intensity and magnetic field.

Answer

Altitude and barometric pressure.

Question 58

What is the **role of coenzymes** in enzyme reactions?

Accepted Answer

To provide additional functional groups, electrons, or metal ions.

Answer

To lower the activation energy of the reaction.

Answer

To increase the enzyme's specificity for its substrate.

Question 59

Which of the following is an example of a **competitive inhibitor**?

Accepted Answer

A molecule that resembles the substrate and competes for binding to the active site.

Answer

A molecule that irreversibly binds to the enzyme and prevents it from functioning.

Answer

A molecule that binds to the enzyme away from the active site and changes its shape.

Question 60

What is the **purpose of feedback inhibition** in metabolic pathways?

Accepted Answer

To regulate and prevent the overproduction of end products.

Answer

To provide energy for the reaction.

Answer

To increase the rate of the reaction.

Answer

To activate the enzymes involved in the pathway.

Question 61

What is the **difference between an exoenzyme and an endoenzyme**?

Accepted Answer

Exoenzymes work outside the cell, while endoenzymes work inside the cell.

Answer

Exoenzymes are more specific than endoenzymes.

Answer

Exoenzymes are smaller than endoenzymes.

Question 62

Which of the following **techniques** can be used to **purify enzymes**?

Accepted Answer

Chromatography, electrophoresis, and precipitation.

Answer

Immunoassay and PCR.

Answer

Distillation and filtration.

Question 63

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

Accepted Answer

It represents the substrate concentration at which the enzyme reaches half of its maximum velocity.

Answer

It is the maximum velocity of the enzyme.

Answer

It is the substrate concentration at which the enzyme is saturated.

Question 64

What is the active site of an enzyme?

Accepted Answer

The specific region of the enzyme where the substrate binds and the catalytic reaction occurs.

Answer

The part of the enzyme that is responsible for recognizing the substrate.

Answer

The entire surface of the enzyme.