Final Exam Mock Questions
1 After 3 years of graduate studies, you have managed to purify a protein to the point where you are able to
crystalise it. At this point, you can assume that the protein is, essentially, pure. You decide to work out how much
of the protein you actually have. Using an online tool (which is not down for website maintenance...) you
determine that the expected extinction co-efficient at 280nm for the protein under your spectrophotometry
conditions is 250 00 M -1 , cm -1 . You prepare 100ul of a 1:10 dilution of your protein and do a spec reading at
280nm; you get a value of 0.153. Given that you have 1ml of the undiluted protein solution and that the protein
has a molecular mass of 150kDa how many micrograms of protein have you wasted spent 3 years isolating?
2 Given the following graph, the formula in the enzyme kinetics documents and that the inhibitor concentration was
4mM, determine Km and Ki for this system (substrate, enzyme, inhibitor).
3 Given the following information and the following enzymes, what enzymes could you use to perform a restriction
digest? What would you expect the sizes of fragments to be? Assume complete digestion of plasmids. Assume
plasmid was ligated into the plasmid using the HindII site. Assume all restriction digest sites are at 425 for ease of
4 NaCl costs $50 for 100 grams.
Na2HPO4 costs $100 for 500 grams.
CH3COOK costs $75 for 200 grams.
Assuming the water is free, how much does 750ml of the following solution cost?
Buffer X= 1.5M NaCl, 0.5M Na2HPO4, 100mM CH3COOK
5 Given the following absorbance values for the ONPG Assay (and different substrate concentration and over time) and
the Bradford Assay for an unknown enzyme D, answer the following questions.
ONPG 405 nm
12 1.743 14 1.854
ONPG 405 nm
Bradford 595 nm
Concentration (ug) Absorbance
a Construct a Michaelis-Menten Curve. Given that the original substrate concentration was 10 mM.
b Construct a Lineweaver-Burk Curve. What is the initial velocity of the reaction? What is the Vmax? What is the
Km of the substance? Does the reaction rate stay constant throughout the experiment?
c Construct the standard curve for the Bradford Assay. Based on the curve, what is the protein concentration?
(Absorbance of sample = 0.578, 10 ul of a 1:15 dilution)
d What is the specific activity of the reaction?
6 Given the following pre and