Enzyme Structure & Function

Question 1

What is the main function of enzymes?

Answer 1

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 2

How do enzymes lower activation energy?

Answer 2

By bringing the reactants together to interact more efficiently.

Enzymes do not change the overall energy of a reaction.

Question 3

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

Answer 3

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 4

What is the structure of enzymes?

Answer 4

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 5

What is the tertiary structure of an enzyme?

Answer 5

The tertiary structure is the complex three-dimensional shape that allows the enzyme to function.

This structure is formed by the folding of the polypeptide chains.

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 are the two models of substrate binding to enzymes?

Answer 7

• 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 8

What is activation energy?

Answer 8

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 9

What happens to enzymes after catalyzing a reaction?

Answer 9

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

Question 10

What does lactase break down?

Answer 10

Lactose disaccharide sugars into glucose and galactose.

Lactose is the sugar found in dairy products.

Question 11

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

Answer 11

Substrate

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

Question 12

What are enzymatic activators?

Answer 12

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

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

Examples: Magnesium activates kinase

Question 13

What are enzymatic inhibitors?

Answer 13

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

Question 14

What is the difference between reversible and irreversible inhibitors?

Answer 14

• 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 15

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

Answer 15

• 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 16

What is substrate specificity in enzyme activity?

Answer 16

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

Question 17

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

Answer 17

The relationship between an enzyme and its substrate.

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 18

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

Answer 18

Vmax

Vmax can be reached when optimal enzymatic conditions are present.

Question 19

How does temperature affect enzymatic activity?

Answer 19

Higher temperatures increase kinetic energy and 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 20

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

Answer 20

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 21

How does pH affect enzyme activity?

Answer 21

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 22

How does substrate concentration affect enzyme activity?

Answer 22

By increasing the reaction rate until saturation is reached.

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 23

What are the three factors that can affect enzyme activity?

Answer 23

• enzyme and substrate concentration
• temperature
• pH levels

Question 24

What are enzymes and what is their role in an organisms’ bodies?

Answer 24

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

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

Question 25

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

Answer 25

Enzyme **regulation** is necessary to **control the activation** of enzymes in which some enzymes are turned on while others are turned off.

Question 26

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

Answer 26

It controls how many enzymes are produced by an organism's body by **inducing or repressing** the gene producing the enzyme. ## Footnote Genetic regulation affects the quantity of enzymes produced based on the body's needs.

Question 27

What is **compartmentalization**?

Answer 27

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 28

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

Answer 28

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

Question 29

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

Answer 29

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 30

What is the mechanism of **covalent modification** in enzyme regulation?

Answer 30

It involves the covalent binding of a singular molecular group to regulate enzymatic activity through **addition** or **subtraction** of the molecular group. ## Footnote By changing the molecular group, enzyme activity is altered.

Question 31

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

Answer 31

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 32

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

Answer 32

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 that production will stop.

Question 33

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

Answer 33

* Competitive inhibition * Uncompetitive inhibition * Non-competitive inhibition

Question 34

What happens in **uncompetitive inhibition**?

Answer 34

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

Question 35

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

Answer 35

**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 they need to catalyze.

Question 36

What is **denaturing** in the context of enzymes?

Answer 36

It is the process where an enzyme **unfolds and loses its shape**. ## Footnote This occurs when ionic bonds are disrupted, preventing the enzyme from functioning.

Question 37

What role do **ionic bonds** play in enzyme structure?

Answer 37

They help the enzyme fold into the **correct** shape. ## Footnote These bonds are formed between positively and negatively charged amino acids.

Question 38

What are the effects of **excess hydrogen ions** on enzymes?

Answer 38

It can **interrupt** ionic bonds, causing enzymes to unfold and **lose their shape**. ## Footnote This disruption can lead to decreased enzyme activity.

Question 39

What is **homeostasis** in relation to enzyme function?

Answer 39

Homeostasis is the **balance of conditions** in the cell needed for proper enzyme function. ## Footnote It is crucial for maintaining optimal concentrations of salts and acids.

Question 40

What happens to enzyme activity when **salt concentrations** are optimal?

Answer 40

Enzyme activity **peaks** when salt concentrations are in their optimal range. ## Footnote This balance is necessary for the enzyme's structural organization.

Question 41

What is **catalase** and its function?

Answer 41

Catalase is an enzyme that **breaks down hydrogen peroxide** into oxygen gas and water. ## Footnote It is found in all living things and is often used in experiments.

Question 42

# Fill in the blanks: Enzymes are made of individual molecules called \_\_\_\_\_\_\_ \_\_\_\_\_\_\_.

Answer 42

amino acids ## Footnote Amino acids are strung together to form polypeptides, which fold into enzymes.

Question 43

What can **disrupt** protein structure besides hydrogen ions?

Answer 43

Salts can also disrupt protein structure by **dissociating** into ions. ## Footnote These ions can interfere with ionic bonds in the protein.

Question 44

How does acid affect **catalase** activity?

Answer 44

Acid disrupts ionic bonds in catalase, **decreasing** its activity. ## Footnote This results in fewer bubbles when hydrogen peroxide is applied.

Question 45

What are some **examples** of enzymes and their **optimal pH**?

Answer 45

* **Pepsin**: Optimal pH 2 * **Amylase**: Optimal pH 7 * **Lactase**: Optimal pH 6.6-6.8 * **Catalase**: Optimal pH 7-11 ## Footnote These enzymes are involved in the digestion of different macromolecules.

Question 46

What are **ribozymes**?

Answer 46

RNA molecules that act as enzymes. ## Footnote Ribozymes are mainly found in viruses, bacteria, and plant organelles.

Question 47

What is the **role** of catalysts?

Answer 47

Substances that increase the rate of a reaction by **reducing activation energy**. ## Footnote Enzymes are often referred to as biological catalysts.

Question 48

What is the **active site** of an enzyme?

Answer 48

The area where the **substrate binds to the enzyme**. ## Footnote The active site is crucial for the enzyme's catalytic activity.

Question 49

What is the **optimal temperature** for enzyme activity in the human body?

Answer 49

37 degrees Celsius ## Footnote This temperature is critical for maximizing enzyme performance.

Question 50

What happens to enzyme activity for every **10-degree rise** in temperature?

Answer 50

**Increases** by 50 to 100% ## Footnote Small temperature variations can significantly impact enzyme performance.

Question 51

What are **thermophilic** enzymes?

Answer 51

Enzymes produced by organisms that grow optimally at **high temperatures**. ## Footnote These enzymes have optimal temperature ranges from 60 to 80 degrees Celsius.

Question 52

What characterizes **psychrotolerant** enzymes?

Answer 52

They have optimal enzymatic activity at **low temperatures**. ## Footnote Psychrotrophic bacteria are examples of organisms that produce these enzymes.

Question 53

# Fill in the blank: Enzymes are also referred to as \_\_\_\_\_\_\_.

Answer 53

catalysts ## Footnote This term highlights their role in speeding up reactions.

Question 54

What are the four main classifications of **macromolecules**?

Answer 54

* Carbohydrates * Lipids * Proteins * Nucleic acids ## Footnote These macromolecules are essential for the functioning of living organisms.

Question 55

What is an **enzyme-substrate complex**?

Answer 55

A structure formed when a substrate **binds** to the **active** site of an enzyme. ## Footnote This complex lowers the activation energy needed for the chemical reaction.

Question 56

What happens to the enzyme after a **reaction** occurs?

Answer 56

The enzyme remains **unchanged** and can **bond again** to another substrate. ## Footnote This allows enzymes to facilitate multiple reactions.

Question 57

What effect does **increasing** enzyme concentration have on reaction rate?

Answer 57

Increasing enzyme concentration generally **increases** the rate of substrate-to-product conversion. ## Footnote This is true only if there are more substrates than enzymes present.

Question 58

What occurs when enzyme concentration **exceeds** substrate concentration?

Answer 58

The reaction rate remains the **same**, as there are not enough substrates for the additional enzymes. ## Footnote This leads to a plateau in the reaction rate graph.

Question 59

What is the relationship between **enzyme concentration** and **enzyme activity**?

Answer 59

As enzyme concentration **increases**, enzyme activity increases until a **plateau** is reached. ## Footnote This plateau occurs when the number of enzymes equals or exceeds the number of substrates.

Question 60

# Fill in the blank: Enzymes lower the \_\_\_\_\_\_\_ required for a chemical reaction to occur.

Answer 60

activation energy ## Footnote This property allows reactions to occur much faster in the presence of enzymes.

Question 61

What is the **significance** of the enzyme-product complex?

Answer 61

It is formed after the enzyme-substrate complex and results in the **release** of the product while the enzyme remains **unchanged**. ## Footnote This complex indicates that the reaction has been completed.

Question 62

What does **pH** measure?

Answer 62

It measures the **concentration of hydrogen ions** in a solution, indicating its acidity, alkalinity, or neutrality. ## Footnote The pH scale ranges from 0 (strongly acidic) to 14 (strongly alkaline), with 7 being neutral.

Question 63

What is the **optimal pH** of an enzyme?

Answer 63

The optimal pH of an enzyme is the **ideal pH value** at which the enzyme's activity is the **highest**. ## Footnote Each enzyme has a specific optimal pH that influences its catalytic efficiency.

Question 64

What happens to enzyme activity when pH is **below** the optimal value?

Answer 64

Enzyme activity **decreases** when the pH falls below the optimal value. ## Footnote This reduction in activity is due to changes in the enzyme's molecular structure.

Question 65

What is the pH range for **acidic** solutions?

Answer 65

The pH range for acidic solutions is from **0 to less than 7**. ## Footnote A pH of 1 is the strongest acid, while 6.9 is the weakest acid.

Question 66

What is the pH range for **basic** (alkaline) solutions?

Answer 66

The pH range for basic solutions is from more than **7 to 14**. ## Footnote A pH of 14 is the strongest base, while 7.1 is the weakest alkaline solution.

Question 67

What is the **lock and key theory** in enzyme activity?

Answer 67

The lock and key theory states that enzymes **bind to specific substrates at their active site**, resembling a lock and key mechanism. ## Footnote This specificity allows enzymes to catalyze only particular reactions.

Question 68

# Fill in the blanks: Enzymes bind with substrates to form an \_\_\_\_\_\_\_ \_\_\_\_\_\_\_.

Answer 68

enzyme-substrate complex ## Footnote The formation of this complex reduces the activation energy required for the reaction.