Practice Plotting a Lineweaver-Burke Graph

Here's the data, calculate the rate with the help of the standard curve. Here are the answers.

[S], mmole/L	Absorbance	Product, mmoles (from Std. curve)
0.005	0.38	0.015
0.002	0.26	0.011
0.00125	0.20	0.0085
0.004	0.35	0.0145

Rate calculations Since you are looking for a rate, you want amount/time. So, divide the amount product/time of reaction. 0.015/15min. = 1 x 10^-3 mmole/min

Rate (V), mmole/min.	1/V, min/mmole	1/[S], L/mmole
1 x 10^-3	1000	200
7.3 x 10^-4	1370	500
5.7 x 10^-4	1754	800
9.7 x 10^-4	1030	250

Graphing

The y-axis should be 1/v and the x-axis is 1/S. You have several choices for making the graph.

You can use a computer- This is probably the easiest, but beware. It can give you false sense of security. Make sure you understand where all the numbers are coming from!

You can use your calculator - you can determine the equation for the line and hand-plot the data and the line. This is the method I recommend. It will teach you a lot, and is usually the least frustrating.

Plot everything by hand - this may be the only option open to some of you. Don't moan and groan too much. You'll understand the LB-plots better than anyone else.

I used my calculator to get the equation (y = 1.28x + 727.7; R=0.999), and plugged the data into my computer graphing software so I could give you a pretty graph.

Kinetic Parameters

Vmax is easy. It is the y intercept, or b (as in y = mx + b) from your equation. Km can be from your graph, the x intercept, or you can calculate it. Remember m = Km/Vmax. So Km = m * Vmax.

Vmax Km

1.37 x 10^e-3 mmole/min 1.76 x 10^-3

There is one pitfall. If you calculate the equation for the line on your calculator, then use that equation for determining Km and Vmax. If you plot the best fit line by eye, then you must determine Km and Vmax from your graph. DO NOT MIX AND MATCH METHODS. Be consistent. Do NOT calculate the equation and then draw in a best fit line and take the Km and Vmax from the graph.