Enzymes

Question 1

What are cofactors

Answer 1

Additional components to aid catalytic activity

Question 2

What are the three types of Co-factors

Answer 2

Metals, Prosthetic groups and co-enzymes

Question 3

Which type of reaction is catalysed by Oxidoreductases

Answer 3

Redox Reactions

Question 4

Which type of reaction is catalysed by Transferases

Answer 4

Group Transfer Reactions

Question 5

Which type of reaction is catalysed by Hydrolases

Answer 5

Hydrolysis reactions

Question 6

Which type of reaction is catalysed by Lyases

Answer 6

Addition/removal of groups to form double bonds

Question 7

Which type of reaction is catalysed by Isomerases

Answer 7

Isomerisation Reactions

Question 8

Which type of reaction is catalysed by Ligases

Answer 8

Ligation reactions of two substrates at the expense of ATP hydrolysis

Question 9

Can Enzymes effect equilibrium

Answer 9

No, they help to reach equilibrium faster

Question 10

What 4 parameters affect enzyme activity

Answer 10

pH
Temperature
Enzyme concentration
substrate concentration

Question 11

How does pH affect enzyme activity

Answer 11

Affects in particular ionisable amino acids
Alters the structure of the active site
Affects catalytic ability or substrate binding ability

Question 12

How does Temperature effect enzyme activity

Answer 12

Increases the rate of enzyme-catalysed reactions
the interactions that determine the 3D shape of the enzyme become disrupted with further increases in temperature
The longer the incubation time, the more noticeable the effects

Question 13

What can impact Thermolability

Answer 13

Mutations that can disrupt the stability in the expected temperature range (denature faster than expected)

Question 14

How does enzyme concentration impact enzyme activity

Answer 14

increasing the concentration of the enzyme increases its activity
This is until the substrate becomes limiting

Question 15

What is the Vmax of an enzyme

Answer 15

The fastest theoretical speed the enzyme can work at

Question 16

What is the Kcat of an enzyme

Answer 16

How many reactions an enzyme can catalyse per unit time (specific to an enzyme)

Question 17

What is the formula to calculate Kcat

Answer 17

Kcat = Vmax/[E]

Question 18

What is the Km of an enzyme

Answer 18

the amount of substrate required to reach 1/2Vmax

Question 19

What is the Km used for

Answer 19

The substrate concentration that most sensitively affects enzyme activity

Question 20

What does lipoprotein lipase do

Answer 20

Releases fatty acids from circulating lipoproteins so that the free fatty acids can be taken up by surrounding tissues
Released by both adipose tissue and skeletal muscle

Question 21

Why does adipose tissues LPL have a high Km

Answer 21

The rate of FA release is dependent on LPL protein levels
After a meal, LPL levels are high
Adipose LPL are highly active, and the free fatty acids released can be stored in the adipose tissue

Question 22

Why does skeletal muscle LPL have a low Km

Answer 22

The rate of FA releases is dependent on the [LPL] as the enzyme is saturated at low LPL levels
After a meal, activity does not increase any further, as the enzyme is saturated
Between meals, the amount of free fatty acids released from LPL id dependant on how much LPL is secreted by the muscle

Question 23

What is co-operativity

Answer 23

When the substrate also binds to another active site on the enzyme, affecting activity

Question 24

What is negative co-operativity

Answer 24

Increased substrate concentration inhibits the activity of the enzyme

Question 25

What is positive co-operativity

Answer 25

When increased substrate activity increases the activity of the enzyme

Question 26

What is Irreversible inhibition

Answer 26

Permanently modifies the enzyme, often covalently
Km unaltered
Vmax decreases

Question 27

What are reversible inhibitors

Answer 27

Inhibitors bind to the enzyme or enzyme complexes via hydrophobic, ionic or van Der Waals intreactions

Question 28

What are competitive inhibitors

Answer 28

Compete with the substrate for the active site of the enzyme
normally have a similar structure
make it more difficult for the actual substrate to bind to the active site
The activity of the enzyme remains unchanged, so the Vmax does not change
more substrate required to achieve results, so the Km increases

Question 29

How do you overcome competitive inhibitors

Answer 29

Increase the concentration of substrate

Question 30

What are statins

Answer 30

used to lower the cholesterol in the blood, in order to prevent CVD

Question 31

How much do statins decrease plasma [LDL]

Answer 31

30-60%

Question 32

What are uncompetitive inhibitors

Answer 32

the binding of the substrate results in the a binding of the inhibitor, forming an unproductive ESI complex
This draws the E/ES equilibrium towards ES.
Lower Km
Lower Vmax

Question 33

What concentration are uncompetitive inhibitors more effective

Answer 33

high substrate concentrations

Question 34

What are non-competitive inhibitors

Answer 34

Inhibitor can bind to either E or ES
doesn't alter binding
prevents catalysis
Decreases the concentration of functional enzyme
Vmax decreases
Km unaffected

Question 35

What are protein kinase inhibitors

Answer 35

Typically ATP competitive inhibitors with low specificity but a high affinity