Topic 2.4 Enzymes

Question 1

What are Enzymes?

Answer 1

Enzymes are biological catalysts that increase the rate of reaction, by lowering the activation energy of the chemical reaction, without being used up.

Question 2

How are enzymes important at a cellular level?

Answer 2

Specific enzymes ensure homeostasis within the cell by tightly regulating the concentration of substances

Question 3

How are enzymes important at a whole-organism level?

Answer 3

Enzyme activity impacts physiological processes such as digestion, respiration, and immune responses

Question 4

Explain how digestive enzymes works.

Answer 4

Digestive enzymes break down macromolecules into absorbable units, for example lactase breaks down lactose into glucose and galactose.

Question 5

Explain how metabolic enzymes works.

Answer 5

Metabolic enzymes facilitate energy production.
For example, hexokinase phosphorylates glucose in the first step of glycolysis.

Question 6

Explain what detoxification enzymes do?

Answer 6

Detoxification enzymes neutralise toxins and drugs.

Question 6

Why is metabolism important?

Answer 6

Metabolism is in charge of all the chemical reactions within an organism

Question 7

What are the two categories of metabolism

Answer 7

• Anabolism
• Catabolism

Question 8

What is the difference between Anabolism and Catabolism?

Answer 8

Anabolism is the building up of molecules whereas catabolism is the breaking down of molecules.

Question 9

What impact do enzymes have on structure

Answer 9

• Enzymes are in processes that determine the structural integrity of cells and tissues
  For example, collagenase helps in remodelingl collagen.
• Enzymes facilitate the synthesis of macromolecules like DNA, RNA, and proteins

Question 10

What impacts do enzymes have on function?

Answer 10

• Enzymes are crucial for functioning processes within cells, and the organism as a whole.
  For example, ATP synthase is important in cellular respirates by synthesising ATP.

-Enzymes like amylase and protease enable to the breakdown of carbs and proteins, providing essential nutrients, in the digestive system.

Question 11

Explain the Lock and Key hypothesis.

Answer 11

An area within the tertiary structure of the enzymes has a specific shape that is complementary to the shape of a specific substrate. This area is called the active site.

When the substrate binds to the active site, an enzyme-substrate complex is formed. The substrate then reacts and the products are formed in the enzyme-substrate complex. The products are then released, leaving the enzyme unchanged and able to take part in subsequent reactions.

Question 12

Explain the Induced-fit Hypothesis.

Answer 12

The initial reaction between the enzymes and substrate is relatively weak, but these weak interactions rapidly induce changes in the enzyme’s tertiary structure that strengthen binding, putting strain on the substrate molecule. The active site of the enzyme changes shape slightly as the substrate enters. This can weaken a particular bond in the substrate, therefore lowering the activation energy for the reaction.

Question 13

Explain Intracellular reactions and enzymes

Answer 13

Intracellular reactions are reactions that occur inside cells, where enzymes help maintain cell function. Enzymes that act within cells are called intracellular enzymes

Question 14

Give an example of Intracellular reactions/enzymes

Answer 14

For example, hydrogen peroxide is a toxic product of many metabolic pathways. The enzyme catalase ensures hydrogen peroxide is broken down into oxygen and water quickly, therefore preventing its accumulation and damage to cells.

Question 15

Explain what Extracellular reactions and enzymes are.

Answer 15

Extracellular reactions are reactions that occur outside cells, often in digestive processes. Enzymes are released from cells to break down these large nutrient molecules into smaller molecules in the process of digestion. These enzymes are called extracellular enzymes.

Question 16

Give an example of Extracellular reactions/enzymes.

Answer 16

For example, amylase is an enzyme secreted by salivary glands and the pancreas into the digestive system. It breaks down starch( a large carbohydrate molecule) into maltose( a smaller sugar molecule) in the mouth and small intestine. This is an essential step in digestion, as it allows the body to absorb and use sugars for energy.

Question 17

How does enzyme concentration affect the rate of enzyme-controlled reactions?

Answer 17

The rate of reaction increases as enzyme concentration increases as there are more active sites for substrates to bind to, however, increasing the enzyme concentration beyond a certain point does not affect the rate of reaction as there are more active sites than substrates so substrate concentration becomes the limiting factor.

Question 18

How does substrate concentration affect the rate of enzyme-controlled reactions?

Answer 18

As the concentration of substrates increases, the rate of reaction increases as more enzyme-substrate complexes are formed. However, beyond a certain point, the rate of reaction no longer increases as enzyme concentration becomes the limiting factor.

Question 19

How does increasing temperature affect the rate of enzyme-controlled reactions?

Answer 19

At increasing temperatures, molecules have more kinetic energy, leading to more frequent collisions between enzymes and substrates, meaning more enzyme-substrate complexes are formed.

The optimum temperature is the temperature at which the enzyme is most active.

Question 20

How does extremely high temperatures affect the rate of enzyme-controlled reactions?

Answer 20

After reaching its optimum temperature, the higher temperatures cause the enzyme’s bonds, more specifically the hydrogen and ionic bonds, to break, altering the enzyme’s tertiary structure and causing the active site to denature. This means the active site is no longer complementary to the substrate and no enzyme-substrate complexes can form.

Question 21

How does pH affect the rate of enzyme-controlled reactions?

Answer 21

Each enzyme has an optimum pH at which it works most efficiently.

Changes in pH affect the ionisation of amino acids in the active site. This disrupts the hydrogen and ionic bonds maintaining the enzyme’s structure, leading to denaturation. The active site loses its specific shape, preventing substrate binding and lowering activation energy.

Question 22

What are Cofactors?

Answer 22

Cofactors are non-protein substances that are essential for the proper functioning of some enzymes. They may be: Inorganic (e.g., metal ions or minerals) or Organic (if they are coenzymes, derived from vitamins).

Question 23

What are Coenzymes?

Answer 23

Coenzymes are a type of cofactor that is an organic molecule. They often act as carriers for chemical groups or electrons during reactions.

Question 24

Give an example of a cofactor.

Answer 24

Chloride ion as a cofactor for amylase: Amylase requires CL- ions to function efficiently. The chloride ion binds to the enzyme and helps maintain its shape or aids in substrate binding, ensuring proper catalysis.

Question 25

Give an example of Coenzymes

Answer 25

Vitamins as a source of coenzymes: Many coenzymes are derived from vitamins. Without adequate vitamins in the diet, enzymes requiring these coenzymes may become inactive.

Question 26

What are Enzyme Inhibitors. Give the 4 types

Answer 26

Enzyme inhibitors are molecules that reduce or stop the activity of enzymes by interfering with substrate binding or catalysis. - Competitive - Non-competitive - Reversible - Irreverible

Question 27

How do competitive inhibitors work?

Answer 27

1. A molecule or part of a molecule that has a similar shape to the substrate of an enzyme can fit into the active site of the enzyme. 2. This blocks the substrate from entering the active site, preventing the enzyme from catalysing the reaction. 3. The enzyme cannot carry out its function and is said to be inhibited. 4. The non-substrate molecule that binds to the active site is a type of inhibitor.

Question 28

How do competitive inhibitors effect reaction rate?

Answer 28

The amount of product formed remains the same, however, the rate at which the product formation occurs decreases. The higher the concentration of competitive inhibitor the lower the reaction rate. Increasing the substrate reverses the effect of competitive inhibitors by out-competing them.

Question 29

How do Non-competitive inhibitors work?

Answer 29

1. The inhibitor binds to the enzyme at a location other than the active site. This alternative site is called the allosteric site. 2. The binding of the inhibitor causes the tertiary structure of the enzyme to change, meaning the active site changes shape. 3. This results in the active site no longer having a complementary shape to the substrate so it is unable to bind to the enzyme. 4. The enzyme cannot carry out its function and it is said to be inhibited.

Question 30

How do Non-competitive inhibitors effect reaction rate?

Answer 30

Increasing the concentration of inhibitor will decrease the rate of reaction further as more active sites become unavailable. Increasing the concentration of enzymes or substrates will not overcome the effect of a non-competitive inhibitor.

Question 31

Explain Reversible inhibitors.

Answer 31

Reversible inhibitors bind to the active site through hydrogen bonds and weak ionic interactions, therefore they do not bind permanently. Reversible inhibitors can either be competitive or non-competitive.

Question 32

Explain Irreversible Inhibitors.

Answer 32

Irreversible inhibitors bind to the enzyme, often at the active site, and denature it. Examples of irreversible inhibitors include heavy metal ions such as mercury and silver, which cause disulfide bonds within the protein structure to break, as a result causing the shape of the active site to change, thus affecting protein activity.