web.pdx.edu/~rueterj/esr621/vvsi_excel.htm
Nutrient Uptake Kinetics
This is a step by step instruction sheet for creating a spreadsheet in Excel that will examine v vs. [S].
This page has been formatted in a single column so that you can make your browser window narrow and still work on Excel to the right.
You should set up like this:
Step 1: set up the named variables
In rows A and B, put the labels Vmax1, Ks1, Vmax2, Ks2, Vmax3, Ks3 as shown.
Then go to the cell just to the right of each, select Inser/Name/Define from the menu bar.
and after the dialog box comes up, just say OK. This means that this cell will be called Pmax.
Do the same for each of the five parameters.
Step 2: Put in the values.
Vmax1=20
Ks1=5
Vmax2=10
Ks2=1
Vmax3=5
Ks3=0.2
Step 3: Making a column of substrate values
Move down the spreadsheet to cell A5. Put "S" in this cell (without the quotes). Below that put in a range of nitrate concentrations from 0 to 50.
Next, highlight this column of light values and name them S (Insert/Name/Define).
Step 4: Putting in the v vx. S equations.
Label the cell B5 "v1".
Type the following string into B6
=Vmax1*S/(Ks1+S)
Do the same thing for v2 and v3
Highlight the top of each column of equations (for example B6), drag down to the number of S values that you entered and then do a Edit/Fill/Down command from the menu.
Step 5: Making a chart.
Highlight the entire region from A5 through the bottom right hand corner of the table you just made. Insert a chart (Insert/Chart).
From this point you will follow the wizard but you need to select the XY (Scatter) and click on the version that puts dots and lines.
When you follow the wizard steps you should eventually get a graph that looks like this.
Part B: Analysis
You might want to examine particular regions of the graph in more detail. You can change the scale by changing the values for S in the column A or by changing the scale on the figure.
To change the scale on the chart:
put your mouse on the X axis and double click
The format axis dialog box will come up and you can change the parameters and then hit OK
Try to figure out:
What combination of Vmax and Ks is best?
Why is that the best combination? Explain.