Introduction to enzymes Flashcards
How is the rate enhancement calculated?
catalysed rate divided by uncatalysed rate
Why will product accumulation not be linear?
- substrate concentration falls
- products may inhibit the enzyme
- enzyme might denature
- reverse reaction becomes more favourable
How is enzyme activity measured?
by increasing the substrate concentration and measuring the accumulation of products over time
How is Vmax and Km calculated?
Lineweaver-Burke Plot
What is Km?
the substrate concentration required for half maximum velocity
How does hexokinase work to phosphorylate glucose?
- has low Km and works at lower concentrations of glucose
- found in all tissues
How does glucokinase work to phosphorylate glucose?
- has a high Km and works at high concentrations of glucose
- predominantly found in the liver
What is irreversible inhibition?
react with the enzyme and form a covalent adduct with the protein
What is competitive inhibition?
competes with the substrate for the active site of the enzyme
Why is there an increase in Km when using competitive inhibition?
a higher concentration of substrate is needed to reach Vmax
What is allosteric inhibition?
bind to the enzyme at the same time as the substrate
What happens to Vmax and Km in allosteric inhibition?
Vmax decreases
Km often increases
