Topic 5: Enzymes And Metabolism

Question 1

What is metabolism?

Answer 1

The sum of chemical reactions that take place in an organism, including catabolism and anabolism.

Question 2

What is catabolism?

Answer 2

The breaking down reactions in an organism, (e.g. respiration). Energy is required.

Question 3

What is anabolism?

Answer 3

The building up reactions in an organism (e.g. hydrolysis, photosynthesis). Energy is released.

Question 4

What is activation energy?

Answer 4

The energy supplied to the reactants before a reaction can occur

Question 5

What is the role of enzymes in metabolism?

Answer 5

Enzymes are present in our body and function as biological catalysts. They lower the activation energy so that chemical reactions take place at body temperature at a faster rate.

Question 6

What is the lock and key hypothesis?

Answer 6

A hypothesis to explain the specificity of enzyme actions: An enzyme molecule only binds to substrate molecules that fit the shape of its active site.

Question 7

Describe the process of a metabolic reaction.

Answer 7

1. A metabolic reaction begins when the substrate molecules bind to the active site of an enzyme to form an enzyme-substrate complex.
2. Its formation lowers the activation energy of the reaction.
3. The substrates are converted into products.
4. The enzyme molecule is released in its original form.

Question 8

What components of an enzyme do the lock and key hypothesis refer to?

Answer 8

The lock refers to the substrate as they are broken down/built up during the process.
The key refers to the enzyme as it does not change during metabolism.

Question 9

What are the properties of enzymes?

Answer 9

1. Enzymes are biological catalysts
2. The actions of enzymes are specific
3. Enzymes are protein in nature
4. Enzymes are reusable
5. Enzymes are needed in relatively small amounts

Question 10

Enzymes are biological catalysts.

Answer 10

Enzymes speed up metabolic reactions by lowering the activation energy of the reactions.

Question 11

The actions of enzymes are specific.

Answer 11

An enzyme only acts on substrates that fit into its unique active site.

Question 12

Enzymes are protein in nature.

Answer 12

The structure and activity of enzymes are easily affected by temperature and pH. They can be denatured.

Question 13

Enzymes are reusable.

Answer 13

Enzymes remain unchanged after reactions. They can bind to other substrate molecules after the reaction is complete.

Question 14

Enzymes are needed in relatively small amounts.

Answer 14

Since enzymes can be reused, they are usually needed in small amounts only.

Question 15

Factors affecting rate of enzymatic reactions (3)

Answer 15

1. Temperature
2. pH
3. Inhibitors

Question 16

What happens when enzymes are exposed to low temperatures?

Answer 16

Enzymes are inactive. The chances for enzyme and substrate molecules to collide together is low.
Less enzyme-substrate complex is formed per unit time.
Therefore, the reaction rate is low.

Question 17

What happens when enzymes are exposed to higher temperatures?

Answer 17

Enzymes are more active.
Both enzyme and substrate molecules move around more rapidly and collide with each other more frequently.
This increases the chances of forming enzyme-substrate complexes.
The reaction rate increases.

Question 18

When will the rate of enzymatic reaction reach its maximum?

Answer 18

At its optimum temperature.

Question 19

What happens when enzymes are exposed to overly high temperatures?

Answer 19

High temperatures may cause confrontational change (a change in shape) of the active site of the enzyme.
The enzyme is denatured.
The substrate molecule cannot fit into the active site of the enzyme (loses catalytic ability permanently).
The rate of enzymatic reaction decreases.

Question 20

What happens when enzymes are exposed to unsuitable pH?

Answer 20

Most enzymes work in a narrow range of pH, best at their optimum pH.
The unsuitable pH will cause the enzyme to be denatured.
The rate of enzymatic reaction decreases.

Question 21

What is an inhibitor?

Answer 21

Inhibitors are chemicals that decrease the rate of enzymatic reactions.

Question 22

Examples of inhibitors?

Answer 22

1. Cyanide
2. Heavy metals (mercury ions, lead (II) ions, copper (II) ions)

Question 23

What are the different types of inhibitors?

Answer 23

1. Inhibitors that are structurally similar to the substrate
2. Inhibitors that are structurally not similar to the substrate

Question 24

How do inhibitors similar to the substrate work?

Answer 24

The inhibitor binds to the active site of the enzyme.
It competes with the substrate for the active site.
The substrate cannot bind to the active site to form enzyme-substrate complexes.

*If the concentration of enzymes increases, the competition relaxes and some enzyme-substrate complexes can be formed.

Question 25

How do inhibitors not similar to the substrate work?

Answer 25

The inhibitor binds to the other side of the enzyme. (NOT active site)
The 3D conformation of the enzyme is changed.
It is no longer complementary to the substrate.
The substrate cannot fit into the active site.
There is no enzyme-substrate complex formation.

Question 26

How are enzymes used in the food industry?

Answer 26

1. Cheese making: Protease from young cows are used to coagulate milk to produce cheese.
2. Fruit juice extraction:
   Pectinase can break down pectin in plant cell walls to increase the yield of juice extraction.
   It can break down pectin in the juice so it looks clear.
3. Liquid-centred chocolate production: Invertase helps break down sugars into soluble forms, so solid sugar fillings turn into liquid upon storage.

Question 27

How are enzymes used for environmental protection?

Answer 27

Biodegradable plastic production: An enzyme extracted from a bacterium shortens the time for a plastic bag to degrade by breaking plastic down.

Question 28

Papain: cosmetics and cooking

Answer 28

Papain breaks down dead cells in skin. It makes skin softer and smoother.

Papain, a protease from papayas, breaks down protein in meat so it becomes softer.

Question 29

Cellulase: biofuel production and stonewashed jeans production

Answer 29

Cellulase breaks down cellulose fibres in jeans to produce a stone washing effect.

Cellulase is used to increase the yield in bioethanol production to break down cellulose in crops to sugars.

Question 30

Proteases and lipases: biological washing powders

Answer 30

Breaks down insoluble proteins and lipids in stains into soluble products to be removed by water.

Question 31

Lysozyme: as drugs

Answer 31

used as a drug to treat bacterial infections by breaking down the cell wall of bacteria.

Question 32

Benefits of using enzymes in the commercial industry?

Answer 32

1. Enzymes speed up chemical reactions: shortens time for mass production
2. Enzymes work under moderate conditions: lowers cost of production
3. Enzymes are specific in action: fewer unwanted products
4. Enzymes are reusable and only needed in small amounts: lowers the cost of production

Question 33

Identify the graph for the enzymatic reactions against temperature.

Question 34

Identify the graph for enzymatic reactions against pH.

Question 35

Identify the graph for enzymatic reactions against inhibitors.

Question 36

What is the significance of enzymatic reactions?

Answer 36

Removing toxic by products in our body.
E.g. toxic hydrogen peroxide is catalysed by catalase into oxygen and water 10^14 times faster.
This prevents it from accumulating and killing our cells.

Question 37

Draw a set up to collect and measure the volume of oxygen released during the reaction.