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USABO Open Exam 2012
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USABO Open Exam 2012
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USABO Open Exam 2012Rank the following biological molecules in order of how readily they diffuse across the
plasma membrane from the most diffusible to the least diffusible.
I. CO2
II. Cl
III. Sucrose
IV. Glycerol
A. I, III, IV, II
B. II, IV, III, I
C. III,II, IV, I
D. I, IV, III, II
E. II, I, III, IV - correct answer-D. I, IV, III, II
You perform a Western blot on two proteins of similar molecular weights (~50kDa) and find
only one band developed on your SDS-PAGE gel. How would you modify your assay to
distinguish the two proteins?
A. Use a lower concentration of acrylamide to raise the resolution of your gel
B. Use a non-ionic detergent to denature your protein
C. Focus your sample isoelectrically on a pH gradient
D. Remove reducing agents like mecaptoethanol or dithiothreitol
E. Switch the anode and cathode on your gel - correct answer-C. Focus your sample
isoelectrically on a pH gradient
When found on the extracellular side of the cell, which of the following classes of membrane
molecules is a marker for the phagocytosis of apoptotic cells?
A. Glycolipid
B. Sphingomyelin
C. Phosphatidylethanolamine
D. Phosphatidylserine
E. Phosphatidylcholine - correct answer-D. Phosphatidylserine
The presence of which of the following amino acids in the channel region of aquaporins
contributes to the electrostatic selectivity to allow water, but not other molecules, to pass
through?
A. Valine
B. Tryptophan
C. Asparagine
D. Methionine
E. Leucine - correct answer-C. Asparagine
, One of your classmates has symptoms of protein deficiency. You suspect that she might
have a mineral deficiency due to her diet of nothing but canned spaghetti. Which of the
following minerals should you test for first?
A. Iron
B. Copper
C. Manganese
D. Molybdenum
E. Sulfur - correct answer-E. Sulfur
A new therapeutic drug can treat the symptoms of the demyelinating disease multiple
sclerosis (MS) by blockage of voltage-gated potassium channels. Neuron action potential
conduction improves because:
A. More potassium is allowed to enter the axon which increases the amplitude of the action
potential
B. The high resting leak of potassium out of the axon is minimized
C. Less potassium is allowed to leave the axon which increases the size and duration of the
action potential
D. Less potassium is allowed to leave the axon which prevents the inactivation of
voltage-gated sodium channels increasing the amplitude of the action potential
E. The resistance of the plasma membrane decreases which increases the amplitude of the
action potential - correct answer-C. Less potassium is allowed to leave the axon which
increases the size and duration of the action potential
Which component of Fick's Law of Diffusion is MOST optimized in the ventilation of fish gills
compared to mammalian lungs?
A. Diffusion coefficient
B. Gradient for diffusion
C. Surface area
D. Path length
E. Temperature - correct answer-B. Gradient for diffusion
Pollen grains were treated with colchicine in culture. The resulting plants were
A. No more than large calluses
B. Dihaploid and fertile
C. Dihaploid and sterile
D. Haploid and sterile
E. Haploid and fertile - correct answer-B. Dihaploid and fertile
Which of the following statements about seeds is FALSE?
A. Coleorhizae are found in monocotyledonous seeds
B. Both monocotlyedonous and dicotyledonous seeds have radicles
C. Both monocotlyedonous and dicotyledonous seeds have a pericarp
D. The coleoptile is found only in monocotyledonous seeds
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