Lecture 11 - measuring and comparing the activity of enzymes Flashcards
what does a progress curve measure
it measures the appearance of product or the disappearance of substrate
what velocity must you always use on a progress curve
initial reaction velocity
what will happen when there is a fixed amount of enzyme, as the substrate increases the reaction rate will
increase in a linear way at first
but as all active sites become occupied = rate of reaction stops increasing
what is the Vmax
maximum velocity possible, when substrate is in excess
what is the Km
the substrate concentration at which V = Vmax / 2
what does a small Km mean
it needs very little substrate to reach half velocity
what are the Michaelis Menten assumptions
- product is not converted back to substrate
- by measuring the initial rate, (S) does not change
on the Lineweaver-Burk plot what is the Y intercept
1/Vmax
on the Lineweaver-Burk plot what is the X intercept
-1/Km
on the Lineweaver-Burk plot what is the slope curve
Km/Vmax
what are the units of Km
same as concentration e.g mmol/L
if an enzyme can act on different substrates will the Km for each be the same or different
each substrate that it acts on will have a different Km
what does a high Km mean
low affinity for substrate
what does a low Km mean
high affinity for substrate
what is the Kcat (turnover number)
the number of substrate molecules converted to product, per enzyme, per unit time, when E is saturated with substrate
