UIUC MCB 450 Exam 1 UPDATED
ACTUAL QUESTIONS AND CORRECT
ANSWERS
What does it mean that water has a high dielectric point? - CORRECT ANSWER its molecules
can surround ions and diminish their attraction for oppositely-charged ions
What is the hydrophobic effect? - CORRECT ANSWER Hydrophobic molecules will
spontaneously aggregate because their aggregation causes an increase in the entropy of the water
molecules as they are not stuck around the hydrophobic molecules
What is Brownian motion? - CORRECT ANSWER random motions of water molecules due to
thermal energy in the water, causing molecules to collide with older molecules and larger particles
What phy and psy torsion angles are not allowed in peptide bonds? - CORRECT ANSWER
45,0
0,0
What are Ramachandran plots? - CORRECT ANSWER Plots of values of allowed phi and psy
values
Where is the intrachain H-bonding in alpha-helices? - CORRECT ANSWER NH in the peptide
bond and the carbonyl oxygen on the residue four aa before it
How is each amino acid related to the next one (structurally)? - CORRECT ANSWER Related
by 1.5 A rise and turn of 100 degrees
How many aa per 360 degree turn? - CORRECT ANSWER 360/100=3.6
How big of a rise (in A) per 360 degree turn? - CORRECT ANSWER 3.6aa * 1.5 A = 5.4 A
How do you calculate length of a peptide? - CORRECT ANSWER # of amino acids * 1.5 A
, Are naturally occurring a-helices right- or left-handed? - CORRECT ANSWER Right-handed
How big is the average a-helix? - CORRECT ANSWER 10 aa, 15 A
What can destabilize an a-helix? - CORRECT ANSWER Adjacent similar charges; bulky
residues close together; Glycine allowing for too much conformational freedom
What stabilizes an a-helix? - CORRECT ANSWER Hydrophobic interactions between
aromatic aa 3 residues apart
Ion pairs between + and - charged aa 2 or 3 aa away
How far apart are aa in a beta sheet? - CORRECT ANSWER 7A
What is the hydrogen bonding system in antiparallel beta strands? - CORRECT ANSWER each
aa is H-bonded to one aa on the adjacent strand
What is the hydrogen bonding system in parallel beta strands? - CORRECT ANSWER each aa
is H-bonded to two aa on the adjacent strand
Why isn't proline favored in beta sheets? - CORRECT ANSWER Can't adopt correct angle and
can't participate in H-bond network due to secondary amine R group
How do you get from one strand to the next in an antiparallel beta sheet? - CORRECT ANSWER
Via B-turns and loops
What two aa are common in B-turns? - CORRECT ANSWER cis-Proline and Glycine
How can globular proteins change conformation? - CORRECT ANSWER Upon binding to a
ligand
ACTUAL QUESTIONS AND CORRECT
ANSWERS
What does it mean that water has a high dielectric point? - CORRECT ANSWER its molecules
can surround ions and diminish their attraction for oppositely-charged ions
What is the hydrophobic effect? - CORRECT ANSWER Hydrophobic molecules will
spontaneously aggregate because their aggregation causes an increase in the entropy of the water
molecules as they are not stuck around the hydrophobic molecules
What is Brownian motion? - CORRECT ANSWER random motions of water molecules due to
thermal energy in the water, causing molecules to collide with older molecules and larger particles
What phy and psy torsion angles are not allowed in peptide bonds? - CORRECT ANSWER
45,0
0,0
What are Ramachandran plots? - CORRECT ANSWER Plots of values of allowed phi and psy
values
Where is the intrachain H-bonding in alpha-helices? - CORRECT ANSWER NH in the peptide
bond and the carbonyl oxygen on the residue four aa before it
How is each amino acid related to the next one (structurally)? - CORRECT ANSWER Related
by 1.5 A rise and turn of 100 degrees
How many aa per 360 degree turn? - CORRECT ANSWER 360/100=3.6
How big of a rise (in A) per 360 degree turn? - CORRECT ANSWER 3.6aa * 1.5 A = 5.4 A
How do you calculate length of a peptide? - CORRECT ANSWER # of amino acids * 1.5 A
, Are naturally occurring a-helices right- or left-handed? - CORRECT ANSWER Right-handed
How big is the average a-helix? - CORRECT ANSWER 10 aa, 15 A
What can destabilize an a-helix? - CORRECT ANSWER Adjacent similar charges; bulky
residues close together; Glycine allowing for too much conformational freedom
What stabilizes an a-helix? - CORRECT ANSWER Hydrophobic interactions between
aromatic aa 3 residues apart
Ion pairs between + and - charged aa 2 or 3 aa away
How far apart are aa in a beta sheet? - CORRECT ANSWER 7A
What is the hydrogen bonding system in antiparallel beta strands? - CORRECT ANSWER each
aa is H-bonded to one aa on the adjacent strand
What is the hydrogen bonding system in parallel beta strands? - CORRECT ANSWER each aa
is H-bonded to two aa on the adjacent strand
Why isn't proline favored in beta sheets? - CORRECT ANSWER Can't adopt correct angle and
can't participate in H-bond network due to secondary amine R group
How do you get from one strand to the next in an antiparallel beta sheet? - CORRECT ANSWER
Via B-turns and loops
What two aa are common in B-turns? - CORRECT ANSWER cis-Proline and Glycine
How can globular proteins change conformation? - CORRECT ANSWER Upon binding to a
ligand
