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Q 1. In this practical exercise you will be using biuret reagent. Why is biuret reagent used in this practical?
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.
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(2 and 4 sentences)
One way in which the experimental procedure could be modified is diluting the sample. This involves decreasing the volume of BSA Protein solution and increasing the buffer volume by the same amount. As a result the absorbance would be lower and fit on the graph. Another way may be to extend the curve by increasing the concentration of the BSA Protein solution which would provide a greater range.

Q 7. Do your results support your hypothesis regarding these tissue samples? (2-3 sentences)
The hypothesis regarding the tissue samples was supported. The absorbance of the sun raised silverbeet plant was found to be 0.801, which was greater than the shaded silverbeet plant with an absorbance of 0.369.

Q 8. One possible reason for the results not supporting your experimental hypothesis is experimental error. List three examples of possible sources of error that may have occurred in your work in this practical class. (2-3 sentences)
A possible error may be adding inaccurate amounts of buffer between samples, causing them to dilute either excessively or insufficiently, resulting in an inaccurate standard curve. Another error could be leaving the sample solutions for over 25 minutes, which could cause the protein to start degrading. Not zeroing the spectrophotometer or cleaning the tube properly can affect the absorbance value.

Q 9. Even if your results do support the experimental hypothesis, give three major possible
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