Enzymes

Question 1

What type of protein are most enzymes?

Answer 1

Globular proteins

Question 2

Most enzymes are globular proteins, what characteristics do they have because of this?

Answer 2

Because of this enzymes are mostly spherical and water soluble

Question 3

Why are enzymes water soluble?

Answer 3

They have to exist in the cell which has an aqueous environment

Question 4

What do most enzymes do?

Answer 4

They make reactions happen quicker i.e. they make biological reactions happen at a rate that sustains life

Question 5

Give three examples of different types of enzymes.

Answer 5

Abzymes
Ribozymes
DNAzymes

Question 6

What do abzymes do?

Answer 6

They speed up reactions of the immune system

Question 7

What do enzymes act on?

Answer 7

Other molecules/substances

Question 8

After a long period of time and many uses, what will happen to an enzyme?

Answer 8

They will wear out and eventually degrade

Question 9

What is the molecule that an enzyme acts on called?

Answer 9

The substrate

Question 10

What is an active site?

Answer 10

The area on an enzyme where a reaction occurs

Question 11

What happens at the active site?

Answer 11

There is a moving around of electrons and the forming/breaking of bonds

Question 12

What is formed when the substrate binds to the active site of the enzyme?

Answer 12

The enzyme/substrate complex is formed

Question 13

What is formed after the enzyme/substrate complex?

Answer 13

The enzyme/product complex is formed

Question 14

What happens after the enzyme/product complex is formed?

Answer 14

The products leave the active site of the enzyme

Question 15

What is the most common type of reaction that occurs to form products?

Answer 15

The substrate is split to form products

Question 16

Describe the relationship between chemical reactions and enzyme reactions.

Answer 16

Enzyme reactions are a specialised type of chemical reaction

Question 17

List four characteristics of a chemical reaction

Answer 17

Reactants converted into products

May involve catalyst

Rate of reaction can be measured

Rate increases as temperature increases without a limit

Question 18

List four characteristics of an enzyme reaction

Answer 18

Substrates converted into products

Always involve catalyst (enzyme)

Rate of reaction can be measured

Rate increases as temperature increases up to a limit

Question 19

What happens to enzymes when a certain high temperature is reached?

Answer 19

Denaturation occurs

Question 20

What happens when an enzyme is denatured?

Answer 20

The active site is lost, there is nowhere for the substrate to bind to -> the reaction cannot occur

Question 21

Give the name of one of the fastest enzymes.

Answer 21

DNase

Question 22

What does it mean if a word end with ‘ase’?

Answer 22

The ending ‘ase’ indicates an enzyme

Question 23

What type of molecule are protein enzymes?

Answer 23

They are polypeptides

Question 24

What are polypeptides?

Answer 24

They are long chains of different amino acids

Question 25

Describe the structure of a polypeptide. | 3

Answer 25

Chain is folded to achieve a specific overall shape Usually looks like a bumpy globe (globular) Surface features based on the different amino acids (side chains)

Question 26

What happens if an enzyme is not folded correctly?

Answer 26

The active site will not be in the correct place, the reaction cannot occur

Question 27

What happens if a substrate doesn't fit in an active site?

Answer 27

The reaction will not happen

Question 28

Describe the structure of the active site. | 4

Answer 28

It has a 3D conformation Amino acids protrude from the surface There is a specific arrangement Amino acids are often charged

Question 29

What keeps the substrate in the active site?

Answer 29

Reactions such as those between oppositely charged areas of the substrate and the active site

Question 30

What is needed for an enzyme/substrate reaction to occur? | 3

Answer 30

Large amounts of the substrate - the more substrate the greater the chance one will come in contact with the activation site Activation energy (Ea) - the energy needed for the reaction to start An enzyme needed to bend the substrate into a shape so the reaction occurs more quickly

Question 31

What is activation energy?

Answer 31

The minimum amount of energy needed for a reaction to start

Question 32

Give an example of one form of activation energy.

Answer 32

It can come in the form of ATP

Question 33

How exactly do enzymes increase the rate of reaction? | 2

Answer 33

They do this by slightly changing the conformation/shape of the substrate so that its more like the product This allows the reaction to occur more easily and therefore increases the rate of reaction

Question 34

What would happen if the substrate 100% rigid and unyielding?

Answer 34

The reaction would not occur

Question 35

What is enzyme kinetics?

Answer 35

Measuring the rates of reaction of enzymes

Question 36

Give two ways we know catalysts do anything.

Answer 36

An increase in product formation A decrease in amount of substrate

Question 37

How do we study enzyme kinetics? | 2

Answer 37

By using a substrate that is practical and convenient to monitor i.e. it is highly coloured or fluorescent, radioactive etc We can then use a spectrophotometer to monitor the reaction

Question 38

Why does the amount of free enzyme decrease?

Answer 38

It decreases as the enzyme/substrate complex is made -> the ES complex increases

Question 39

What happens as the amount of substrate decreases?

Answer 39

The amount of product increases

Question 40

What does the Michaelis-Menten Equation allow us to do?

Answer 40

It allows us to calculate the expected velocity at a given [S] as we have established the Vmax and Km for an enzyme/substrate reaction pair

Question 41

What is the Michaelis-Menten Equation?

Answer 41

Velocity = Vmax [S]/Km + [S]

Question 42

What is the common rule of thumb for the relationship between temperature and rate of reaction?

Answer 42

That a 10 degrees increase in temperature doubles the rate of reaction (this only happens up to a certain point for enzyme reactions)

Question 43

What is actually happening in enzyme inhibition?

Answer 43

The enzyme cannot complete a catalytic cycle

Question 44

What is formed in enzyme inhibition?

Answer 44

An enzyme inhibitor complex is formed (EI complex)

Question 45

What are the two forms of an EI complex?

Answer 45

Reversible of irreversible | two types of inhibition

Question 46

What happens in reversible inhibition? | 3

Answer 46

The inhibitor can bind to and dissociate from the enzyme Activity is lost when the inhibitor is bound Must wait for the enzyme to become free to overcome this inhibition

Question 47

What happens in irreversible inhibition? | 2

Answer 47

The enzyme is covalently modified and the activity is lost Must replace the enzyme to overcome this inhibition

Question 48

What are the three forms of reversible inhibition?

Answer 48

Competitive Uncompetitive Mixed

Question 49

What happens in competitive inhibition? | 2

Answer 49

The inhibitor binds at the active site This prevents the substrate from binding

Question 50

What happens in uncompetitive inhibition? | 2

Answer 50

The inhibitor bind to the enzyme-substrate complex This does not happen at the active site

Question 51

What happens in mixed inhibition?

Answer 51

The inhibitor can bind to the free enzyme of the enzyme substrate complex

Question 52

How does pH influence enzyme activity?

Answer 52

By altering amino acid structure - particularly those in the active site