Chem 153A - Lec 2 Midterm #1 Form D
Vivian Wong
TOTAL POINTS
66 / 100
QUESTION 1
Question 1: Peptide and titration curve
26 pts
1.1 Draw peptide 10
... [Show More] / 10
+ 4 Termini and peptide bonds are correct
+ 6 All amino acid side chains are correctly drawn
+ 1 N-terminus is correctly drawn
+ 1 C-terminus is correctly drawn
+ 1 Carbonyl is correct in peptide bond
+ 1 N-H is correct in pepetide bond
+ 2 Histidine is drawn correctly
+ 2 valine is drawn correctly
+ 2 glutamate is drawn correctly
+ 0 Incorrect/Blank
1.2 Q1 B-D 5 / 5
+ 1 His is imidazole
+ 1 Val is an alkane/methyl/propyl
+ 1 Glu is carboxylic acid/carboxyl
+ 1 C: correct net charge based on their peptide
(should be -1)
+ 1 20^3
+ 0 Incorrect/Blank
1.3 Titration Curve 7 / 8
+ 1 direction: going down from ~14 to ~0
+ 1 0.5 eq points are shallowest part of the curve
+ 1 Full eq points are steepest part of the curve
+ 1 a 0.5 eq pt at pH = 8.5
+ 1 a 0.5 eq pt at pH = 6
+ 1 a 0.5 eq pt at pH = 4.2
+ 1 a 0.5 eq pt at pH = 3.5
+ 1 Buffer ranges are +/- 1 unit of graphed pKas and
labeled on the graph with brackets
+ 0 Incorrect/Blank
+ 1 a 0.5 eq pt at pH = 3.7 based on your above
peptide
+ 0.5 a 0.5 eq pt at 9.5 (instead of 8.5)
+ 0.5 a 0.5 eq pt at 2 (instead of 3.5)
+ 1 a 0.5 eq pt at pH = 10.5 based on above peptide
1.4 pI 3 / 3
+ 1 pKas used are in numerical order from their
titration curve
+ 1 average included 6.0
+ 1 average included 4.2
+ 1 Average Included 3.7 based on peptide above
+ 0 Incorrect /Blank
QUESTION 2
Question 2: Protein Structure 28 pts
2.1 A and B secondary H-bond 6 / 8
+ 2 A: Hydrogen bonds
+ 1 B: Drew a Hydrogen bond
+ 1 B: H-bond include N-H
+ 1 B: H-bond includes C=O
+ 1 N-H is correctly identified on the backbone
+ 1 C=O is correctly identified on the backbone
+ 1 that N-H and C=O are in the correct position to
form a H-bond
+ 0 Incorrect/Blank
2.2 C and D tertiary structure 6 / 6
+ 1 C: side chain of serine is correct
+ 1 C: facing the outside of the helix
+ 1 C: coming from an alpha carbon
+ 1 C: At the first alpha carbon from the N-terminal
side of the peptide (the bottom alpha carbon)
+ 1 D: Valine is in the core of the protein
+ 1 D: Serine would be near the surface of the
protein
+ 0 Incorrect/Blank
2.3 E Thermodynamics 4 / 7 [Show Less]