Download Bio302 Biochemistry II,

Bio302 Biochemistry II,
Midterm Examination 1, March 27, 2002
Questions 1-10, each 5 points, Questions 11-18 each 10 points.
Answer only FIVE of the questions among 11-18.
Question 1.
Protein kinases
a) use Thr, Ser, or Tyr as the acceptor groups for phosphoryl transfer.
b) transfer the a (alqha) phosphorus atom of ATP.
c) are located on the external surface of cells.
d) transfer a phosphoryl group from one protein to another.
e) use AMP as substrate.
Question 2.
Protein kinase A
a) is activated by ATP
b) consists of two C (catalytic) and two R (regulatory) subunits in the absence of
activator.
c) upon binding the activator dissociates into one C2 and two R subunits.
d) contains a pseudosubstrate sequence in the C subunits.
Question 3.
A. Describe the mechanism of activation for the zymogens below. Give also the
names of their active forms and where they are located:
a) Pepsinogen
b) Trypsinogen
c) Chymotrypsinogen
d) Proelastase
e) Procarboxypeptidase
B. How the active forms of the above zymogens are inactivated?
Question 4.
Which of the properties listed below are characteristics of a peripheral or an integral
protein.
a) bind to the surface of membranes
b) have transmembrane domains
c) require detergents fo dissociation from the membrane
d) require mild salt or pH treatment for dissociation from the membrane
Question 5.
For the following structures below, write down
a) which are phosphoglycerides?
b) which is a glycolipid
c) which contain sphingosine?
d) which contain choline?
e) which contain glycerol
Question 6.
For a bacterium moving toward an increasing concentration of an attractant, which of
the following statements are correct?
a) tumbling will be more frequent
b) tumbling will be less frequent
c) The clockwise rotation of flagella will occur more frequently.
d) The counterclockwise rotation of flagella will occur more frequentlly.
Question 7.
The methyl-accepting chemotaxis proteins
a) may bind attractants or repellents directly
b) may interact with soluble, periplasmic chemosensors.
c) Are reversibly methylated in the periplasmic domain.
d) Are reversibly methylated in the cytosolic domain.
e) have common periplasmic domains in each of the four proteins in this family.
Question 8.
Which of the following are the second messengers that are produced by the
phosphoinositide cascade?
a) Phosphatidyl inositol 4,5-bisphosphate.
b) Inositol 1,3,4-trisphosphate
c) Inositol 1,4,5-trisphosphate
d) Inositol 4-phosphate
e) Inositol 1,3,4,5-tetrakisphosphate
f) Diacylglycerol
Question 9.
True or false? Receptor tyrosine kinases
a) Are integral membrane enzymes.
b) Are often activated by ligand-induced dimerization
c) Can phosphorylate themselves on their cytoplasmic domains when activated by
their ligands.
d) Are seven-helix transmembrane receptors.
e) Activate their targets via G proteins.
Question 10.
Why do membrane proteins not flip-flop across membranes?
Answer only the FIVE of the questions below. Each 10 points.
Question 11.
Describe how one could prepare a liposome for the purpose of transporting a watersoluble drug to specifically targetted to a particular type of cells.
Question 12.
Distinguish between channels and pumps with respect to selectivity, energy
requirement and speed. List the forms of energy that can drive active transport.
Question 13.
Explain the ion selectivity of the acetylcholine receptor channel. Compare Na+, K+
and Cl-
Question 14.
Draw a Schiff base. (Show an attaching group (show as R) is Schiff based to an amino
acid side chain on a protein.)
Question 15.
Describe the role of sodium-calcium exchanger. Compare its capacity to transport
Ca2+ with the Ca2+-ATPase.
Question 16.
Describe how restoration of the dark state is achieved, following the light induced
changes in retinal cell. (outline the enzymatic cascade for adaptation to light)
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Question 17.
What evidences might implicate that cAMP is a second messenger?
Question 18.
Define oncogene and relate oncogene function to G proteins. Give an example.