CHEM 224 Carbohydrate Structures Mini Chemistry Exam 3

Chem 224 Mini Exam 3 sum 2021By taking this exam, I acknowledge and agree to the following:
1. I certify that work in this exam is solely my work. I did not receive input from another individual.
2. I accept the consequences of academic dishonesty.
3. This exam is open-book and open-note and you may use a molecular model kit, but no other resources are allowed.
Name ____________________________ Student ID______________________________
You have 60 minutes for this exam. You will take the exam using 1 of the 3 following options:
1. print the exam and complete it with a pen
2. write directly on the pdf file with your computer
3. write your answers on blank sheets of paper. These sheets MUST follow the EXACT same layout as the exam – 1 cover
sheet and then 7 pages of questions (you don’t need the chart of amino acids).
You are NOT permitted to post this exam on any website.
Regardless of how you take the exam, you will then convert your exam into a pdf file and upload it to canvas by 2.35pm
without penalty, The canvas assignment link closes at 3pm. There is a late penalty (15%) if the exam is uploaded
between 2.35-3pm.
The Exam must be uploaded as one pdf file (not multiple pages). You do not need to include the last page of amino acid
structures.
Also, keep in mind the point value for each question when you allot time to each question. Work should be shown for all
questions, incorrect answers without any work will not be awarded any credit, Likewise, showing your work drastically
increases the odds of you receiving partial credit. If an explanation question gives a sentence limit, please keep to that.
Question
1
Points Possible
14
2
14
3
9
4
18
5
12
6
10
7
8
8
15
Total (100
For Q1-6)
100
Points Received
1
1) Fill in the carbohydrate structures below. To help, the chair templates and Fisher projections are started
for you, you are given the Fischer projection for idose and cyclic form of altrose (14 pts).
a) (3 pts) Fischer projection for L-gulose:
b) (4 pts) Pyranose form of -D-idose
c) (3 pts) Is the chiral center highlighted with red arrow in pt b. R, S or achiral? ___________
d) (4 pts) Fischer projection for D-altrose
2
2. Answer the following for the carbohydrates depicted below (1-8)
a. (4 pts) Which are/is considered ‘D’ sugars?__________
b. (4 pts) Which of the structure(s) are hemiacetals?_________
c. (6 pts) Match the cyclic form (1-4) with it’s Fisher (open chain) form (5-8)
For #1 the Fisher / open chain is__________
HOCH2
HO
OH
OH
HO
OH
OH
HO
O
CH2OH
O
HO
H
H
OH
OH
H
4
H
OH
O
H
H
O
OH
HO
H
H
H
OH
H
OH
HO
H
OH
H
OH
H
OH
H
OH
H
OH
H
OH
5
OH
OH
3
CH2OH
O
CH2OH
O
HO
HO
2
1
HOCH2
HOCH2
CH2OH
O
O
For #4 the Fisher / open chain is__________
H
CH2OH
6
HO
CH2OH
7
H
HO
H
H
OH
OH
H
CH2OH
8
3) Consider lysine, glutamic acid, and histidine.
a) (9 pts) Draw the appropriate ionization states for each amino acid at pH 5. To do this, circle any
portions of the amino acid that need to be changed, and draw the correct form of that functional
group next to the circle. The pKa of the His side chain is 6.4.
Example:
3
4) Give the major product(s) or reactants of the following 4 reactions. If there is no reaction, write “NR”.
Notes are provided for some parts. (18 pts total)
a) (4 pts)
b) (5 pts) (don’t worry about stereochemistry for this part)
Boc
O
HN
OH
1) DCC
2) CF3COOH, H2O
and
O
H2N
CH3
O
HO
c) (3 pts)
O
–
O2C
aminotransferase
CO2
–
PLP
oxaloacetate
4
d. (6 pts) Circle 2 of the amino acid derivatives below that you would use to synthesize the dipeptide shown.
O
Boc
H2N
OCH3
O
HN
OH
O
O
1) DCC
H2N
Boc
O
N
H
2) CF3COOH, H2O
3) NaOH, H2O
O
OH
SH
HN
OH
HS
H2N
OCH3
HS
5. (12 pts) Draw the structure of the tetrapeptide Gly-Tyr-Phe-His at pH 5. (see last page for Amino acid
structures) The pKa of the Tyr side chain is 10, The pKa of the His side chain is 6.4
Be sure to show:
All the appropriate charges that would be present.
List the N-terminus and C-terminus.
Draw an arrow → to the peptide bonds and show their correct geometry
5
6) Draw the curved arrow mechanism for the following transformations. (10 pts, 5 pts each)
H
O
OH
H
OH
H
H
+
HO
H
HO
H
H , H2O
O
H
H
HO
H
OH
OH
CH2OH
b) When drawing the mechanism use ‘Ad’ instead of writing out the entire adenosine molecule
NH2
glucose
H
O
O
+
H
–
O
H
HO
H
H
N
ATP
OH OH
P
O
O
–
OH
P
O
–
O
N
O
P
O
O
H
OH
N
O
–
O
N
H
H
OH
H
H
Ad
O
O
P
OH
O
–
O
H
O
H
H
HO
H
H
OH
OH
+ ADP
6
7. State if the processes below are Anabolic (A), or Catabolic (C) (8 pts total, 2 pts each)
a Glucose being converted to acetyl CoA during Glycolysis______
b. Protein hydrolysis to form amino acids ________
c. Glucose molecules combining to form complex carbolydrates _______
d. Overall process that has a large + G value ________
8. Answer the following questions in one or two sentences.
a) (3 pts) What does it mean that the amino acid Lysine is considered ‘Ketogenic’.
b) (3 pts) What intermolecular interaction is involved in the formation of the secondary structures (-helices
and -sheets)
c) (5 pts) Which aldolhexose(s) when reduced with NaBH4 would produce an ‘achiral’ sugar alcohol? Show the
reduced product(s).
d) (4 pts) -glucose differs from both -glucose and -galactose by a single chiral center. When -glucose is
dissolved in acidic water, some -glucose is formed, but not -galactose. Explain this difference of reactivity.
-glucose
-glucose
-galactose
7
Carbohydrate and Amino acid charts
8