Worksheet 4
Biological Molecules
25 points
Name:
Section:
Date Turned In:
Introduction:
1. (3 pts) Compare and contrast the indicators used in this lab (Benedict’s, Iodine,
Sudan, Biuret). Make sure to include the concept of quantitative/qualitative data
in your answer.
2. (3 pts) Compare and contrast the functional groups of a monosaccharide, a fatty
acid, and an amino acid.
Materials and Methods:
3.. (2 pts) We performed a negative control of distilled water and iodine solution.
Why is it important to perform a negative control before testing the mystery
solutions?
4. (2 pts) Look at the absorbance spectrum on the last page. At what wavelength
would you set the spectrophotometer if you wanted to detect the lowest
%transmittance? Explain your answer.
5. (2 pts) Methods matter to results! Go to the lab website. Click on Molecules,
Genes, Cells Lab and the follow the link under Topic 4: Worksheet Question 5.
Assume that cuvette A was prepared as a demonstration by your lab instructor, so
it has no errors. Clearly explain the reasons why tubes B-E would give results that
will not match cuvette A.
Results:
6. (3 pts) For each of the listed unknown solutions, provide experimental evidence
that demonstrates that it is NOT fat free milk. Circle the letter or letters of
solutions that could be fat free milk.
Evidence against fat free milk
Unknown A
Unknown B
Unknown C
Unknown D
Unknown E
7. (5 pts) Using Prism, construct a standard curve for the protein concentration
data. Include a linear regression line and properly format the graph. (note: you
should “force the line to go through 0 and 0” when selecting the options for the
linear regression). Include a properly formatted figure legend that explains why the
line must be forced through 0 and 0.
Discussion:
9. (2.5 pts) Use the standard curve of class average data to determine the protein
concentration of Protein X. Use correct units. .
Protein X concentration:
10. (2.5 pts) Using your standard curve. If Protein Y has a concentration of
3.5mg/ml, what absorbance do you predict it will have? Use correct units.
Class Average Absorbance
0.6
0.5
0.4
0.3
0.2
0.1
0
350
400
450
500
550
600
650
Wavelength (nm)
Lowest %T wavelength that best detects solution =
700
750
800