Biochemistry II
CHEM 471B
Whittier College
Department of Chemistry
Problem Set #3
Due Tuesday, April 20 @ 5:00 p.m.
You may work in groups. Each group can turn in one set of answers for all members of the group. Ensure that each member of
the group signs the submitted homework page. Each student is responsible for emailing me (dstoub@whittier.edu) a distribution
of 100 points between the members of the group (if four people worked equally on the problem set, each member would give each
other 25 points). IF YOU DON’T DO THIS YOU WILL LOSE 10 POINTS!
Part A.
Do problems 2, 3, 10, 11 & 16 of your book (page 810-811).
Part B.
1. Why is it effective for a bacterial cell to organize genes for related functions as an operon? How do
eukaryotes achieve the same benefit?
2. The enzyme known as ribonuclease H (RNAse H) cleaves the RNA portion of a RNA-DNA hybrid
helix.
a. Structural studies of RNAse H indicate that the active site is nestled in a cluster of Lys
Residues. What is the probable function of these Lys residues?
b. RNAse H does not bind double stranded DNA, single-stranded DNA or single-stranded
RNA. It binds double-stranded RNA but does not cleave it. What does this reveal about the
substrate conformation required for binding and hydrolysis?
3. Explain why the vast majority of nucleic acids with catalytic activity are RNA rather than DNA?