1.4.2 Enzymes

Question 1

Enzymes are described as biological catalyst, what does this mean

Answer 1

Biological- means produced by living tissue
Catalyst- means speeds up the rate of reaction and they don’t get changed by the reaction

Question 2

What is a catabolic enzyme

Answer 2

An enzyme that breaks down large molecules into smaller ones

Question 3

What is an anabolic enzyme

Answer 3

An enzyme that builds up smaller molecules into larger molecules

Question 4

What type of protein is an enzyme

Answer 4

Globular protein

Question 5

Enzymes don’t cause reactions to happen, instead they do what to reaction

Answer 5

They speed up reactions that were already taking place

Question 6

What is the name of the specific region of the enzymes

Answer 6

The active site

Question 7

Is the enzymes’ active site made from many or few amino acids

Answer 7

Relatively few amino acids

Question 8

What is the name given to the molecule that the active site acts upon

Answer 8

Substrate

Question 9

What is formed when an enzyme and substrate fit neatly

Answer 9

An enzyme-substrate complex

Question 10

The enzyme is ——- to the substrate (fill in blank)

Answer 10

Complementary

Question 11

What are the 2 locations of enzyme action

Answer 11

• Intracellular
• Extracellular

Question 12

In intracellular enzyme action, what are the 3 organelles in which enzymes are located

Answer 12

• Lysosomes
• Cytoplasm
• Mitochondrial membrane

Question 13

In extracellular enzyme action, what is the main system in which enzymes action occurs

Answer 13

Digestive system, alimentary canal

Question 14

What is an exergonic reaction

Answer 14

A reaction which releases energy

Question 15

What is an endergonic reaction

Answer 15

A reaction which requires energy

Question 16

How do enzymes catalyse a reaction

Answer 16

By lowering the activation energy

Question 17

Name the 2 enzyme action theories

Answer 17

• Lock and key mechanism
• Induced fit

Question 18

What forms when a substrate binds to an enzyme

Answer 18

Enzyme-substrate complex

Question 19

A substrate bust be complementary in —— to the active site (fill in the blank)

Answer 19

In shape

Question 20

How does the induced fit model describe the active site

Answer 20

That it’s not quite complementary in shape but then moulds to the shape of the substrate

Question 21

In the induced fit model, what happens to the active site once the products are released

Answer 21

They go back to their original shape, so they’re unaltered by the reaction

Question 22

True or false: enzymes are generally large complex fibrous proteins

Answer 22

False, they are globular

Question 23

True or false: the active site forms only a small part of the whole enzyme and is highly specific for its substrate

Answer 23

True

Question 24

True or false: Enzymes increase the rate of reaction by lowering the activation energy of the reaction

Answer 24

True

Question 25

True or false: The formation of an enzyme-substrate complex makes the substrate more stable

Answer 25

True

Question 26

True or false: In the induced fit model, the enzyme and its active site change shape when the substrate binds

Answer 26

True

Question 27

True or false: Enzymes can catalyse reactions that would not otherwise occur

Answer 27

False

Question 28

True or false: Anabolic reactions involve the break down of large substrates into smaller ones

Answer 28

False, catabolic reactions break down, anabolic build up

Question 29

True of false: Endergonic reactions require an intake of energy

Answer 29

True

Question 30

True or false: ATP hydrolysis is an endergonic reaction

Answer 30

False, its an exergonic reaction

Question 31

True or false: Enzyme action in the alimentary canal is an example of intracellular digestion

Answer 31

False, its an example of extracellular

Question 32

What is the equation to calculate rate when the dependent variable is time

Answer 32

1/ Time (in seconds)

Question 33

What is the unit for rate of reaction when the dependent variable is time (2 answers)

Answer 33

s ^-1 s^-1 x 10^-3

Question 34

What is the calculation for rate of reaction when the dependent variable is mass or volume

Answer 34

Volume/ time (in seconds) Mass/ time (in seconds)

Question 35

What are the 4 factors that affect enzyme action

Answer 35

- Temperature - pH - Substrate concentration - Enzyme concentration

Question 36

On a rate of reaction against temperature on an enzyme action graph, why does the graph initially increase

Answer 36

Because there is an increase in kinetic energy of both enzymes and substrates so there is an increase of successful collisions so there is an increase in enzyme-substrate complexes formed so there is more product formed in a certain period of time

Question 37

On a rate of reaction against temperature on an enzyme action graph what does the peak of the graph mean

Answer 37

The optimum temperature

Question 38

On a rate of reaction against temperature on an enzyme action graph why does the graph decrease after the peak

Answer 38

Because the amino acids which make up the protein begin to vibrate so the hydrogen bonds between the R groups begin to break so the tertiary structure of the enzyme changes shape which in turn alters the shape of the active site- denaturing the enzyme so the substrate is no longer complementary so fewer enzyme-substrate complexes form so fewer products are produced per period of time

Question 39

In extreme pH what type of bonds in the enzyme are broken

Answer 39

Ionic bonds

Question 40

What is an enzyme inhibitor

Answer 40

A molecule that interferes with/ slows down enzyme activity

Question 41

What are the 2 types of enzyme inhibitors

Answer 41

- Competitive - Non- competitive

Question 42

Can maximum rate of reaction still be achieved when a competitive inhibitor is present

Answer 42

Yes, when you increase the substrate concentration

Question 43

How does a competitive inhibitor work

Answer 43

By binding to the active site so fewer enzyme-substrate complexes form per unit of time

Question 44

How does a non-competitive inhibitor work

Answer 44

It binds somewhere other than the active site, known as the allosteric site, which changes the tertiary structure, so changes the shape of the active site preventing substrate from binding, fewer enzyme-substrate complexes form

Question 45

What is a metabolic pathway

Answer 45

A series of reactions in which each step is catalysed by an enzyme

Question 46

Describe the induced-fit model of enzyme action and how an enzyme acts as a catalyst (3 marks)

Answer 46

- Substrate binds to the active site - Active site changes shape slightly so it is complementary to substrate - Reduces activation energy

Question 47

A competitive inhibitor decrease the rate of an enzyme-controlled reaction. Explain how. (3 marks)

Answer 47

- Inhibitor similar shape to substrate / complementary to active site - Binds to active site - Reduces enzyme-substrate complex forming

Question 48

Explain how the active site of an enzyme causes a high rate of reaction (3 marks)

Answer 48

- Lowers activation energy - Induced fit causes the active site to change shape - So enzyme-substrate complex causes bonds to form/break

Question 49

Describe how a non-competitive inhibitor can reduce the rate of an enzyme-controlled reaction (3 marks)

Answer 49

- Attaches to the enzyme at a site other than the active site - Changes shape of the active site - So active site and substrate no longer complementary so less substrate can bind

Question 50

Formation of an enzyme-substrate complex increases the rate of reaction. Explain how. (2 marks)

Answer 50

- Reduces activation energy - Due to bending bonds / without enzyme, very few substrates have sufficient energy for reaction

Question 51

Describe how an enzyme can be phosphorylated (2 marks)

Answer 51

1. Attachment/association of (inorganic) phosphate (to the enzyme); 2. (Released from) hydrolysis of ATP OR (Released from) ATP to ADP + Pi;

Question 52

Suggest one advantage to a bacterium of secreting an extracellular protease in its natural environment. Explain your answer (2 marks)

Answer 52

1. To digest protein; 2. (So) they can absorb amino acids for growth/reproduction/protein synthesis/synthesis of named cell component; OR (So) they can destroy a toxic substance/protein;

Question 53

Describe the action of membrane-bound dipeptidases and explain their importance (2 marks)

Answer 53

1. Hydrolyse (peptide bonds) to release amino acids; 2. Amino acids can cross (cell) membrane; OR Dipeptides cannot cross (cell) membrane; OR Maintain concentration gradient of amino acids for absorption; OR Ensure (nearly) maximum yield from protein breakdown;