The biuret reagent is used to assess the concentration of the protein because peptide bonds occur with the same frequency per amino acid in the peptide. The intensity of the colour, and therefore the absorption, is directly proportional to the protein concentration.
Q 2. What is the experimental reason for constructing a standard curve?
Multiple samples with known properties can be measured and graphed, which then enables the same properties to be determined for the unknown samples, in this case the concentration, by interpolating the graph which depicts the relationship between the absorbance and concentration.
Q 3. Based on the above information (in the prac manual) and your own thinking, which plant do you hypothesize will have more rubisco, one raised in the sun or one raised in shade?
It is hypothesised that the sun raised silverbeet plant will have more rubisco than the shaded silverbeet plant.
Q 4. Should the line connect all the data points or should it be a line of best fit? Why? (2 sentences)
A line of best fit as it will give an accurate representation of the relationship between absorbance and concentration between the different samples. The more samples used, the closer the results would be to the line of best fit.
Q 5. Is it possible to determine the protein concentration of a solution from the standard curve if the measured absorbance is off the scale of the y-axis, i.e. higher than the highest y-value on the standard curve? Give your reasons. (4 sentences)
It’s not possible to determine the protein concentration because the data gathered from the standard solutions is in a certain range (specific scale). Therefore the relationship between absorbance and concentration cannot be determined for anything outside of this range.
Q 6. Describe two ways in which you would modify the experimental