Excel Enzyme exercise for 4105 Fsbmol 2016 PDF

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Excel Enzyme exercise for 4105FSBMOL 2016 - 2017 Lineweaver-Burk The Michaelis constant KM, and the maximal rate Vmax, can be readily derived from rates of catalysis measured at different substrate concentrations if an enzyme operates according to: k1

E +

S

k3

ES

E

+

P

k2

It is convenient to transform the Michaelis-Menton equation into one that gives a straightline plot, i.e. 1 1 K 1   M  V Vmax Vmax [S] where:

[S] is the concentration of uncombined substrate, Vmax is the maximal rate when enzyme sites are saturated with substrate V is the rate of catalysis A plot of 1/V versus 1/[S], called a Lineweaver-Burk plot yields a straight line with intercept of 1/Vmax and slope of KM/Vmax. Using the following data plot a Lineweaver-Burk plot and determine Vmax and KM. Data Table [S] (µM)

Velocity ( M/min)

No inhibitor Inhibitor 3.0 10.4 2.1 5.0 14.5 2.9 10.0 22.5 4.5 30.0 33.8 6.8 90.0 40.5 8.1 HINT: - Investigate the use of INTERCEPT & SLOPE to determine Vmax and KM Use of excel for y=mx + c straight line graphs, logs and pH. Straight line graphs can be described using the formula y=mx + c, where m is the gradient (slope) and c is the intercept, sometimes called b (as in excel). Excel can be used to plot straight-line graphs and various values can then be calculated LINEST this calculates the statistics for a line by using least squares method. It returns an array onto your worksheet. syntax: =LINEST(known_ys,known_xs,const,stats) 1

e.g. =LINEST(B1:B5,C1:C5,FALSE) Would determine the gradient of the data in columns B and C and the use of “false” forces the gradient through 0 i.e. y=mx TREND this returns values along a linear trend. Fits a straight line (using the method of least squares) to the arrays known_ys and known_xs. Returns the y-values along that line for the array of new_xs that you specify. syntax: =trend(known_ys,known_xs,new_xs, const) const is a logical value, TRUE then the intercept is calculated, FALSE then b is set to 0. You can add a trendline to a graph by constructing a graph, then selecting it and clicking the RHMB, add trendline should come up, if you select this you can then by using the options display the equation on the chart, force the intercept to be 0 and find out what the R 2 value is (closer to 1 better) If you do not want to plot a graph but have data in tables then you can use SLOPE and INTERCEPT. SLOPE this returns the slope of the linear regression line through data points in known_ys and known_xs. The slope is the vertical distance divided by the horizontal distance between any two points on the line, which is the rate of change along the regression line. syntax: =SLOPE(known_ys, known_xs) Note If know_ys or know_xs are empty or have a different number of data points, SLOPE returns the #N/A error message. Also you cannot force through zero – use The known_ys and known_xs can either be cell references or values. eg, =SLOPE({2,3,9,1,8,7,5},{6,5,11,7,5,4,4}) gives a value of 0.305556 or the values could be in cells and then you would enter =SLOPE(A2:A8,B2:B8).

INTERCEPT this calculates the point at which a line will intersect the y-axis by using existing x-values and y-values. syntax: = INTERCEPT(known_ys,known_xs) Note If known_ys or known_xs are empty or have a different number of data points, INTERCEPT returns the #N/A error message.

Also in the tools menu there is also data analysis, here you can find correlation, regression etc.

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