Steady-State Kinetics Interpreter

Design the experiment, read the plot, and work out the constants. Then check them against the true values.

Mode

1Experimental conditions

Reaction

[E]_total

[S] range to

Fixed [B] levels curves, from to µM

Data points

Error in data %

Fit equation Non-linear least-squares fit

Advanced conditions

Temperature °C

Rate units

[S] spacing

Error model

Answer tolerance ± % of the true value

2Plot

Equation

Zoom or drag a box on the plot; double-click to reset

Data table

Try this

Set the error to 0 with the fit off. Estimate V_max and K_m by eye from the Michaelis–Menten plot, then read them from the Lineweaver–Burk intercepts. Do they agree?
Turn the fit on, raise the error to 8%, and press Repeat experiment several times. On which linear plot do the points scatter furthest from the fitted line, and which data points are responsible?
Lower the top of the [S] range until the curve no longer bends. How confident are you in V_max now? Redesign the range to fix it.
Double [E]_total. Which of your answers change, and which stay the same?
Open Advanced conditions and raise the temperature by 10 °C. What happens to V_max and k_cat? Does K_m change, and why?
Switch to Bi Bi and compare the ordered and ping-pong mechanisms on Lineweaver–Burk. Which gives parallel lines? Use the replots to find K_mB.
In Uni Uni, k₁ is given. Use it with your K_m and k_cat to find k₋₁, then compare K_S with K_m. Now switch to ordered Bi Bi: which rate constants can no longer be found? Tick “cannot be determined” for those and check.

3Your analysis

Tutor Edit any true value; the others update to stay consistent. Show fitted values to students

Steady-State Kinetics Interpreter v1.0 · CochranLearning.com