Biochemistry I Fall Term
Calculations & Graphing
Topic #4: Enzyme Kinetics Calculation
Recommended problems in Campbell, Chapter 5: #21, 22, 24.
E + S <=> (ES<->EP) --> E + P
We want to determine Vmax and KM by measuring the dependence of the initial velocity on the substrate concentration. This is done in three steps.
(Each calculated vo value has a small "experimental error" added to it.
- The Michaelis-Menten equation is:
vo = Vmax[S]/(KM + [S])
- vo = the initial velocity;
- Vmax = the maximal velocity;
- [S] = the substrate concentration;
- KM = [S] at half-maximal velocity, i.e.the Michaelis constant.
Tabbing out of the [A] entry slot or clicking anywhere on the page will also calculate vo.)
3. Record the values of [S] and vo you obtain; then graph them on a double reciprocal plot to determine KM and Vmax. You should get enough data so as to have 3 or 4 values of vo, both above and below the KM value.
(Hint: Graph the values you obtain as they are calculated; then as the shape of the curve becomes apparent, choose values for [S] that fall into the appropriate range.)
Answers to this problem.
A sample Answer Sheet for a similar problem shows the format of the results and the graph required.
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