Enzymes

Question 1

What are enzymes?

Answer 1

Enzymes are biological catalysts regulating biological processes in living organisms

Enzymes are proteins that facilitate various biochemical reactions.

Question 2

What determines the specific function of an enzyme?

Answer 2

The protein nature and tertiary structure of an enzyme

The tertiary structure is crucial for the enzyme’s active site shape.

Question 3

What types of reactions do enzymes catalyse?

Answer 3

Enzymes catalyse intracellular and extracellular reactions

These reactions are essential for the structures and functions of cells and organisms.

Question 4

What is the role of enzymes in activation energy?

Answer 4

Enzymes lower the activation energy required for chemical reactions

Lowering activation energy increases the rate of reaction.

Question 5

What is activation energy?

Answer 5

The energy required for chemical reactions to take place

Activation energy must be overcome for a reaction to occur.

Question 6

How do enzymes lower activation energy?

Answer 6

By forming enzyme-substrate complexes

This process stabilizes the transition state of the reaction.

Question 7

What is enzyme specificity?

Answer 7

Enzymes are specific to substrates; some act on a single substrate while others target specific chemical bonds

This specificity is due to the unique tertiary structure of each enzyme.

Question 8

What model was initially used to describe enzyme action?

Answer 8

The Lock and Key model

This model suggested that the active site of the enzyme is rigid and fits specific substrates like a key fits a lock.

Question 9

What model has replaced the Lock and Key model?

Answer 9

The Induced-fit model

This model proposes that the active site can change shape to better fit the substrate.

Question 10

Fill in the blank: Enzyme specificity is a feature of the unique _______ structure of an enzyme.

Answer 10

tertiary

The tertiary structure is crucial for the enzyme’s ability to bind substrates.

Question 11

True or False: The shape of the active site is considered fixed in the Induced-fit model.

Answer 11

False

The Induced-fit model suggests that the active site can change shape to accommodate substrates.

Question 12

What does the Induced Fit model suggest about the active site of an enzyme?

Answer 12

The active site is flexible and can slightly change its shape to become complementary to the substrate

Question 13

How does the Induced Fit model explain the interaction between an enzyme and its substrate?

Answer 13

The presence of the correct substrate induces a change in the shape of the active site, allowing it to mold around the substrate

Question 14

What happens to the enzyme at the end of a reaction according to the Induced Fit model?

Answer 14

The enzyme remains unchanged

Question 15

What is the significance of the active site in enzyme reactions?

Answer 15

The active site allows the substrate to bind and facilitates the reaction

Question 16

What is V max in the context of enzyme reactions?

Answer 16

V max is the maximum rate of reaction achieved when all active sites are occupied by substrate

Question 17

What effect does increasing substrate concentration have on the rate of enzyme reactions?

Answer 17

Initially increases the rate of reaction until a maximum rate is reached, after which it levels off

Question 18

What occurs when all active sites of an enzyme are occupied?

Answer 18

The active sites are saturated, and the rate of reaction is limited by enzyme concentration

Question 19

What is required to increase the rate of reaction at higher substrate concentrations?

Answer 19

The addition of more enzyme

Question 20

True or False: The concentration of substrate affects the frequency of collisions between substrate and enzyme molecules.

Answer 20

True

Question 21

What happens to the rate of product formation as the concentration of substrate decreases over time?

Answer 21

The rate of product formation decreases due to less frequent collisions

Question 22

Fill in the blank: The terms associated with enzymes that are essential for exam answers include ‘active site’, ‘complementary’, ‘________’, and ‘tertiary structure’.

Answer 22

denaturation

Question 23

What type of bonds should be mentioned in the context of enzyme reactions?

Answer 23

Disulfide bonds and other specified bonds

Question 24

What is the graphical representation of enzyme-controlled reactions typically show?

Answer 24

The concentration of product formed changes over time

Question 25

What occurs to the concentration of product when all substrate has been converted?

Answer 25

The concentration of product levels off

Question 26

What happens to the rate of reaction when enzyme concentration increases with excess substrate?

Answer 26

The rate of reaction increases due to more active sites available. ## Footnote More enzyme molecules lead to more enzyme-substrate complexes being formed.

Question 27

How does low temperature affect enzyme efficiency?

Answer 27

Enzymes are less efficient as the rate of reaction is slowed down due to reduced kinetic energy. ## Footnote Fewer collisions occur between enzyme and substrate molecules.

Question 28

What effect does increasing temperature have on enzyme activity until the optimum temperature is reached?

Answer 28

Increased temperature provides more kinetic energy, resulting in more collisions and enzyme-substrate complexes. ## Footnote This increases the rate of reaction.

Question 29

What happens to enzymes when the temperature exceeds the optimum level?

Answer 29

The tertiary structure of the enzyme denatures, leading to a decrease in the rate of reaction. ## Footnote Hydrogen and ionic bonds are broken.

Question 30

What is the consequence of denaturation of proteins at temperatures above 50°C?

Answer 30

Denaturation is usually permanent and the substrate cannot bind to the active site. ## Footnote The tertiary structure is irreversibly altered.

Question 31

At what temperature do enzymes exhibit low kinetic energy according to the graph?

Answer 31

At 25°C, enzymes exhibit low kinetic energy. ## Footnote The reaction proceeds at a slow rate due to fewer collisions.

Question 32

What occurs at 37°C regarding enzyme activity?

Answer 32

At 37°C, the reaction proceeds at a faster rate due to more frequent collisions between enzyme and substrate. ## Footnote All substrate is converted into product.

Question 33

What happens to the reaction at 60°C?

Answer 33

The reaction initially proceeds very fast but eventually stops due to enzyme denaturation. ## Footnote Substrate cannot bind to the altered active site.

Question 34

Fill in the blank: An increase in temperature results in more _______ between the active site of enzymes and substrate molecules.

Answer 34

collisions

Question 35

True or False: The rate of reaction is at a maximum at the optimum temperature.

Answer 35

True

Question 36

What is the effect of pH on enzyme activity?

Answer 36

Enzymes possess an optimum pH at which the rate of reaction is at a maximum. ## Footnote Most enzymes are active over a narrow pH range, and extreme pH changes can cause denaturation.

Question 37

What happens to enzymes when the pH deviates from the optimum?

Answer 37

Very different pHs from the optimum can cause denaturation. ## Footnote The change in pH alters the ionic charges of acidic and basic groups.

Question 38

How does a change in pH affect the enzyme's structure?

Answer 38

Hydrogen and ionic bonds are broken, altering the tertiary structure and shape of the active site. ## Footnote This prevents the substrate from binding.

Question 39

What are enzyme inhibitors?

Answer 39

Chemicals that can act as enzyme inhibitors, slowing down the rate of enzyme-catalyzed reactions. ## Footnote They can be competitive or non-competitive.

Question 40

What are competitive inhibitors?

Answer 40

Inhibitors with a similar structure to the normal substrate that compete for attachment to the active site. ## Footnote Their presence reduces the rate of reaction.

Question 41

How can competitive inhibition be reduced?

Answer 41

By adding more substrate, which can outcompete inhibitor molecules for attachment to the active site. ## Footnote At high substrate concentrations, the substrate effectively reduces the impact of the inhibitor.

Question 42

What is the relationship between substrate concentration and the rate of reaction in the presence of a competitive inhibitor?

Answer 42

The rate of reaction decreases as the inhibitor occupies the active site, but can increase with more substrate. ## Footnote The graph illustrates this relationship.

Question 43

Fill in the blank: Enzymes are most active at their _______.

Answer 43

[optimum pH]

Question 44

True or False: Competitive inhibitors increase the rate of reaction by binding to the active site.

Answer 44

False ## Footnote Competitive inhibitors decrease the rate of reaction by occupying the active site.

Question 45

What is a non-competitive inhibitor?

Answer 45

A non-competitive inhibitor is not similar in structure to the substrate.

Question 46

Where does a non-competitive inhibitor bind?

Answer 46

It combines at a position other than the active site.

Question 47

What effect does a non-competitive inhibitor have on the enzyme's active site?

Answer 47

It alters the tertiary structure and shape of the active site.

Question 48

Why can't the substrate attach to the altered active site in the presence of a non-competitive inhibitor?

Answer 48

The active site is no longer complementary to the substrate.

Question 49

What determines the degree of inhibition by a non-competitive inhibitor?

Answer 49

The degree of inhibition is completely dependent on the amount of inhibitor present.

Question 50

Does a high concentration of substrate reduce non-competitive inhibition?

Answer 50

No, a high concentration of substrate will not reduce non-competitive inhibition.

Question 51

Fill in the blank: A non-competitive inhibitor changes the shape of the active site when _______ is present.

Answer 51

[non-competitive inhibitor]

Question 52

True or False: Non-competitive inhibitors bind to the active site of the enzyme.

Answer 52

False

Question 53

What happens to the rate of reaction in the presence of a non-competitive inhibitor?

Answer 53

The rate of reaction decreases compared to when no inhibitor is present.