Question

please answer 1 and 2

1. Determine the protein concentrations for your positive and negative control and your test sample (Table 4) using the protein standard curve you constructed. Include Table 4 and your protein concentrations in your response. Do these results seem accurate to you? Did they differ from what you expected for the food item you brought into class? 2. What is the R2 value of your known protein concentrations plotted against their absorbency? Is the value close to 1? Would you say that the two variables are closely correlated and your standard curve is a reliable tool for using one variable to predict the other? What would it mean if your R was not close to 1?

table 4

protein concentrations

Answer 1

The standard curve fits the straight line equation of Y = 0.106x + 0.0433.

This equation can be used to find value to X-ordinates (protein concentrations) given Y co-ordinate by transforming in the following manner; X = (y – 0.0433)/0.106

For sample with abs 0.071, protein concentration= (0.071 -0.0433)/0.106 = 0.26

For sample with abs 2.71, protein concentration= (2.71 -0.0433)/0.106 = 25.15

For sample with abs 0.0117, protein concentration= (0.0117 -0.0433)/0.106 = -0.298; gives negative vale, means the protein concentration is very low or doesn’t have protein as compared to the standard concentrations.

These results may not be accurate as the absorbance values do not lie in the linear range of the standard curve (absorbance values range from 0.15 to 1).

Estimated protein concentration	Absorbance
-0.298	0.0117
0.26	0.071
25.15	2.71

The standard curve has an R² value of 0.98 which is very close to 1. An R² value closer to 1 indicates that there is a linear relationship between variables of x-axis and y-axis. If x-axis variable changes by a factor, we can predict the value of y-axis as they have linear relationship. This will serve as a reliable tool to predict the unknown protein concentrations when absorbance values in the range are given.

If R² is not closer to 1 that indicates that we are not sure of a linear relation between x-axis (protein concentration) and y-axis (absorbance) variables. We cannot reliably predict the change in one variable given a respective change in other one.