Name__________________________ Lab Instructor____________________
Principles of Biology - Problem Set I
Bio-Chemistry
Answer all of the following questions and turn in to your lab instructor by Thursday 9/9 4pm sharp.
You are welcome and encouraged to work in groups to learn, but you must turn in your own work.
1. You have just ordered some 15N - ammonium sulfate, a good nitrogen source that you can feed to
bacteria so that they will incorporate 15N in their proteins. You wish to conduct experiments using 15N
isotopically labeled proteins that can be detected by an instrument called NMR for structural studies. a)
How many protons, neutrons and electrons does 15N have? b) Compare this to the more common 14N. c)
Do you predict 13N to be a radioisotope? Why or why not. d) Do you think the bonding properties of
15N will be the same or different than common 14N. Briefly explain in one sentence. (4pts)
2. Magnesium chloride is a common reagent that molecular biologists add to their reactions in order to
synthesize DNA, such as a PCR reaction (polymerase chain reaction). We will be running PCR
reactions in a few weeks in lab. The magnesium is important for stabilizing the reactants (nucleotides).
a) Draw the electron shell diagram for magnesium and an electron shell diagram for chlorine. b) Based
on the electron properties, how many bonds does magnesium like to make? Write out magnesium
chloride’s chemical formula. c) Do you think that this compound will be soluble in water? Briefly
explain in one sentence. (3pts)
1
