Undergraduate Exam Biochemistry

1. Finals
Biochemistry 1
12/15/2016
Points 100
1. Deamination of cytosine will produce
a) guanine
b) uracil
c) purine
d) adenine
2. The siRNAs that are currently in clinical trials include both unmodified and chemically
modified forms of RNA; the latter are designed to
a) enhance nuclease resistance
b) greatly increase serum half-lives
c) enhance functional activity
d) a and b
3. Challenges facing RNAi therapy would include
a) Delivery of the molecule since RNAse could easily degrade the molecule
b) Uptake into
4. What happens in automated Sanger DNA sequencing reaction if you forget to add
a) all fluorescent ddNTPs? b) fluorescent ddGTP? c) all dNTPs? d) dGTP
5. In the chemical synthesis of DNA,
a) the dimethoxytrityl (DMT) group catalyzes formation of the phosphodiester bond.
b) the direction of synthesis is 5' to 3'.
c) the maximum length of oligonucleotide that can be synthesized is 8–10
nucleotides.

2. d) the nucleotide initially attached to the silica gel support will become the 3' end of
the finished product.
e) the protecting cyanoethyl groups are removed after each step.
6. tRNA is
a) adapter molecule that is covalently linked to amino acid at one end.
b) pairs with mRNA so that amino acids can be joined to growing polypeptide correctly
c) Held in a complex with rRNA
d) A and b
7. The sugar in DNA with a C-3 endo pucker is found in
a) B-form of DNA
b) A form of DNA that has a wider and flatter helix
c) In RNA double helices
d) B and c
8. PUFAs are
a) Omega 3 fatty acids
b) Suppress cytokines
c) Possess pro-inflammatory activities
d) A and b
e) All of the above
9. Myristic acid in nutmegs acts as a lipid anchor in biomembranes. What is the utility of
having lipid anchors?
10 How does snake venoms affect the red blood cells of its victims?
11. Sequencing of lung epithelial cells reveals a mutation that changes lys-arg-histidine
sequence to a Phe-leu-val in the ion channel that allow anions to leave the cells. The
aquaporin channels are normal. What would be the consequences?

3. . 12. Shown below is a lipid monolayer found in archaea that lives in hot springs. Name
the types of linkage in the lipid shown below and explain why are these linkages important?
13. A) Name the lipid shown above. (b) Where is this lipid found? (c) What is its
function?
14. a) Of the 2 fatty acids shown above, which one will be preponderant in a camel’s cell
membranes that spends most of its time in the serene deserts of Saudi Arabia? (b) Why?

4. 15. Lipid droplets in fat cells can be stained by
a) Oil Red O stain
b) Geimsa stain
c) Gram stain
d) Brown paper towel
16. Match the following (6points)
A Vitamin A 1 Signaling Molecule
B Vitamin D 2 Antioxidant
C Vitamin E 3. Role in calcium
absorption
D Thromboxane A2 4 Prevents blood clotting
E Warfarin 5 Promotes blood clotting

5. 17. In the above diagram, why are detergents not used to remove peripheral
proteins?
18. Clathrins are major proteins that shape rounded vesicles which play critical roles
in the intracellular trafficking and uptake of substances such as LDL and
transferrin in cells.

6. How would defects in clathrin function due to mutations affect intensity of
signaling?
19. Why do the membranes in the organelles shown above have variable
composition of lipids and cholesterol?
20. Membrane fusion is involved in
a) Endocytosis
b) Exocytosis of vessels carrying neurotransmitters
c) Uptake of sugars by Glut 4 transporters
d) A and b

7. e) All of the above
21. P-glycoproteins or ABC transporters
a) use ATP to drive drugs out of cells
b) are part of the efflux mechanism
c) can be used by both prokaryotes and eukaryotes
d) all of the above
22. The acetylcholine receptor is a
a) Tyrosine kinase activator
b) Ligand-gated ion channel
c) G-protein coupled receptor
d) None of the above
23. Cell membranes of many eukaryotes contain
a) Cholesterol
b) Ergosterol
c) Phytosterol
d) hoganol
24. Shown above, what is a function of lipid rafts?

8. 25. Caveolins shown above are proteins that produce membrane curvature. In the
diagram above, what specific function(s) can be attributed to cholesterol in the
process?
26. Signaling cascades can be terminated by
a) receptor desensitization
b) the action of phosphatases
c) GDP hydrolysis
d) Phosphodiesterase activation
e) A, b, and d

9. 27. The signaling system shown above is used by
a) adrenaline
b) GDP hydrolysis
c) GTP hydrolysis
d) Phosphodiesterase activation
e) A, c, and d
28. Insulin signals by
a) GPCRs
b) Receptor tyrosine kinase
c) Activating IRS-1
d) Both b and c
e) None of the above
29. Cytokines and retinol(Vitamin A) signal via
a) GPCRs
b) JAK-STAT pathway
c) Receptor tyrosine kinases
d) Integrins
e) All of the above

10. 30. Integrins
a) Are bidirectional cell adhesion receptors
b) Are Cytosolic proteins
c) Bind collagen and fibronectin
d) A and c
e) All of the above
31. Mouse DNA hybridizes more extensively with human DNA than with yeast
DNA. Explain by describing the factor or factors that determine extent of
hybridization.
32. What could be the biochemical basis of side effects from supplementations of
fat-soluble vitamins?