Enzyme Kinetics Flashcards
1
Q
What are enzyme kinetics and why are they important?
A
- Study of reaction rates and conditions that affect them
- Important for drug development
2
Q
What do Vmax and Km describe?
A
- Vmax - maximal reaction velocity at saturation
- Km - affinity of specific enzyme for substrate
3
Q
What happens to Km when 1/2 of Vmax is reached?
A
Km = substrate concentration
4
Q
How is reaction rate of enzymatic reactions often measured?
A
- Initial velocity measured at a known substrate concentration
- Repeated with different substrate concentrations
5
Q
What does it mean when Km is low?
What does it mean when Km is high?
A
- Low Km - high affinity for substrate
- Opposite for high Km
6
Q
A linear version of a graph of substrate concentration against reaction rate is known as a Lineweaver-Burk plot.
How would you calculate Km and Vmax from this graph?
A
- Vmax - intersection of straight line with y-axis
- Km - intersection of straight line with x-axis
7
Q
Describe Km and Vmax in competitive inhibition.
A
- Vmax unchanged but Km increases
- Because inhibition reversible with high substrate concentration
8
Q
Describe Km and Vmax in non-competitive inhibition.
A
- Vmax decreases but Km unchanged
- Because inhibitor binds to enzyme away from active site.
- So not reversed by increasing substrate concentration
9
Q
Describe Km and Vmax in uncompetitive inhibition.
A
- Vmax and Km decrease
- Enzyme-substrate complex blocked from forming product
10
Q
Describe glucokinase
A
- Low Km and Vmax
- Used during low glucose
- Allosterically regulated by glucose 6-phosphate
11
Q
Describe hexokinase
A
- High Km and Vmax
- Used with large amounts of glucose
- Activated by insulin
- Inhibited by glucagon
12
Q
What do the following enzymes do?
- OXIDOREDUCTASES
- TRANSFERASES
- HYDROLASES
- LYASES
A
- OXIDOREDUCTASES - catalyse redox reactions
- TRANSFERASES - transfer of functional groups to different molecules
- HYDROLASES - catalyse hydrolysis
- LYASES - catalyse bond breaking without oxidation
