2A3 Enzymes and their Importance

Question 1

What are enzymes and what is their role in an organism’s body?

Answer 1

These are naturally produced proteins that act as biological catalysts, speeding up chemical reactions in organisms’ bodies by breaking down substrates into smaller products.

Enzymes bind to substrates, complex molecules that enter cells and upon which enzymes act.

Question 2

What is the main function of enzymes?

Answer 2

To lower the activation energy of a chemical reaction.

Enzymes allow reactions to proceed at a biologically relevant rate.

Examples: The breakdown of foods in the human stomach, such as the action of pepsin on proteins from food sources like animal products

Question 3

How do enzymes lower activation energy?

Answer 3

By bringing the reactants together to interact more efficiently.

Enzymes do not change the overall energy of a reaction.

Question 4

What are the four main steps needed for enzymes to function?

Answer 4

1. Enzyme and substrate must be available in sufficient quantities.
2. Enzyme and substrate collide and bind at the active site.
3. Formation of enzyme-substrate complex.
4. Enzyme releases the product and is available for binding with additional substrate.

The enzyme is not altered during the reaction, allowing it to function multiple times.

Question 5

What is the structure of enzymes?

Answer 5

Proteins bonded together to form a polypeptide chain with a tertiary structure.

Enzymes have an active site where the substrate binds, leading to a conformational change that catalyzes the reaction.

Question 6

What is an active site?

Answer 6

Represents the cleft, or open space, to which the substrate binds.

Once a substrate binds to the active site of an enzyme, the chemical reaction may begin.

Question 7

What is the substance or molecule on which an enzyme functions?

Answer 7

Substrate

Together with enzymes, substrates form an enzyme-substrate complex.

Question 8

What are the two models of substrate binding to enzymes?

Answer 8

• Induced fit
• Lock and key

Induced fit: the active site on the enzyme changes shape in order to bind with its substrate.

Lock and key: This substrate binds to a specific enzyme to activate it- much like a key opens a specific lock.

Question 9

What is substrate specificity in enzyme activity?

Answer 9

The ability of an enzyme to determine which substrate(s) to bind with over the course of a reaction.

Question 10

What is activation energy?

Answer 10

The minimum amount of energy needed for a reaction to proceed in the forward direction.

Enzymes lower the activation energy of a reaction, so that a lower amount of energy is required for the reaction to take place.

Question 11

What happens to enzymes after catalyzing a reaction?

Answer 11

Enzymes are not consumed in a reaction; they simply help it to occur.

Question 12

What does lactase break down?

Answer 12

Lactose disaccharide sugars into glucose and galactose.

Lactose is the sugar found in dairy products.

Question 13

What are enzymatic activators?

Answer 13

Molecules that can increase the activity of an enzyme, such as cofactors and coenzymes.

Some enzymatic activators are known as ‘Essential Enzymatic Activators’ and are necessary for enzyme activity to occur.

Examples: Magnesium activates kinase

Question 14

What are enzymatic inhibitors?

Answer 14

Enzymatic inhibitors are molecules that interact with enzymes and reduce their affinity for their substrate, used for pharmacological purposes.

Question 15

What are the three types of inhibition methods in enzyme regulation?

Answer 15

• Competitive inhibition
• Uncompetitive inhibition
• Non-competitive inhibition

Question 16

What is the difference between competitive and non-competitive inhibitors?

Answer 16

• Competitive inhibitors bind the enzyme at its active site, preventing substrate binding.
• Non-competitive inhibitors bind to another site on the enzyme, altering the conformation of the active site.

Question 17

What happens in uncompetitive inhibition?

Answer 17

The inhibitor binds to the complex formed between an enzyme and its substrate.

Question 18

What is the difference between reversible and irreversible inhibitors?

Answer 18

• Reversible inhibitors cause a rapid dissociation of the enzyme-inhibitor complex and can be overcome with an increase in substrate concentration.
• Irreversible inhibitors cause a slow dissociation of the complex and cannot be overcome by an increase in substrate concentration.

Question 19

What is the Michaelis constant in enzyme activity?

(Km)

Answer 19

Km represents the substrate concentration at which an enzyme works at half its maximum rate.

High Km value = low affinity between an enzyme and its substrate, meaning more substrate is necessary for the reaction to reach its maximum rate.

Low Km value = high affinity between an enzyme and its substrate, meaning less substrate is necessary for the reaction to reach its maximum rate.

Question 20

What is the term for the maximum rate of a reaction that an enzyme can reach?

Answer 20

Vmax

Vmax can be reached when optimal enzymatic conditions are present.

Question 21

What are the three factors that can affect enzyme activity?

Answer 21

• Enzyme and substrate concentration
• Temperature
• pH levels

Question 22

How does temperature affect enzymatic activity?

Answer 22

Higher temperatures increase kinetic energy, resulting in greater enzymatic activity.

You do not want the temperature of a reaction to be too high as denaturation will occur within the enzyme.

In the human body, the optimal temperature for enzyme activity is 37°C (98.6°F).

Question 23

What happens to enzyme activity at temperatures greater than 50°C?

Answer 23

Protein denaturation occurs, rendering the enzyme inactive.

When denaturation occurs, the enzyme undergoes a structural change in shape that makes it unable to recognize its substrate or catalyze a reaction.

Question 24

How does pH affect enzyme activity?

Answer 24

Enzymes function optimally within a specific pH range, and deviations from this range can lead to enzyme inactivity.

In the human body, the optimal pH for enzyme activity is 7.

Question 25

How does **substrate concentration** affect enzyme activity?

Answer 25

By increasing the reaction rate until saturation is reached. ## Footnote The more of a substrate there is, the more enzymes it can bind to. However, once saturation occurs and all the enzymes have been bound with a substrate the reaction cannot occur any faster.

Question 26

Why should all enzymes not be activated at the same time or in the same cell?

Answer 26

Enzyme regulation is necessary to control the activation of enzymes, with some turned on while others are turned off.

Question 27

What is **genetic regulation** in enzyme activity?

Answer 27

It controls how much of an enzyme a cell produces by turning specific genes on or off depending on the cell’s needs. ## Footnote Genetic regulation affects the quantity of enzymes produced based on the body's needs.

Question 28

What is **compartmentalization**?

Answer 28

Enzymes are regulated by compartmentalization, where they are separated by cellular membranes into specific 'compartments', restricting their movement and function to that compartment. ## Footnote Compartmentalization provides the right environment for enzymatic activity and occurs mostly in eukaryotic cells.

Question 29

What is **substrate concentration's** role in enzyme regulation?

Answer 29

It controls the availability of substrates for enzymes to bind and break down, thus regulating enzyme activation.

Question 30

How does **enzymatic degradation** regulate enzyme activity?

Answer 30

It regulates the number of enzymes available by breaking down enzymes themselves or substrates. ## Footnote Degradation of enzymes controls the availability of enzymes for binding with substrates.

Question 31

How does **temperature** affect enzyme activity?

Answer 31

Enzyme activity increases with temperature up to an optimal point, after which high temperatures can denature the enzyme and stop its function.

Question 32

How does **allosteric regulation** control enzymatic activity?

Answer 32

By regulatory molecules binding to an enzyme's allosteric site, changing its shape and function. ## Footnote Changing the shape of the enzyme affects the shape of its active site, where enzymes bind to substrates.

Question 33

What is **feedback inhibition** in enzyme regulation?

Answer 33

Occurs when the product of a metabolic pathway acts as a regulator, inhibiting the enzyme's activity. ## Footnote Example: Production of ATP. The body will continue to produce ATP until the concentration of ATP in the body is high enough production will stop.

Question 34

What are **zymogens** and how are they activated?

Answer 34

Inactive forms of enzymes that require a chemical modification to become active. This modification is often performed by other enzymes, activating the zymogen. ## Footnote Other enzymes need to activate the zymogens and "instruct" them on what the reaction is that they need to catalyze.