A. I, III, IV, II - Solutions Rank the following biological molecul...

USABO Open Questions with Complete Solutions Rank 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

• II, I, III, IV - Correct Answers ✅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?

• Use a lower concentration of acrylamide to raise the

resolution of your gel

• Use a non-ionic detergent to denature your protein
• Focus your sample isoelectrically on a pH gradient
• Remove reducing agents like mecaptoethanol or

dithiothreitol 1 / 3

USABO Open Questions with Complete Solutions

• Switch the anode and cathode on your gel - Correct

Answers ✅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?

• Glycolipid
• Sphingomyelin
• Phosphatidylethanolamine
• Phosphatidylserine
• Phosphatidylcholine - Correct Answers ✅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?

• Valine
• Tryptophan
• Asparagine
• Methionine
• Leucine - Correct Answers ✅C. Asparagine 2 / 3

USABO Open Questions with Complete Solutions 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?

• Iron
• Copper
• Manganese
• Molybdenum
• Sulfur - Correct Answers ✅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:

• More potassium is allowed to enter the axon which

increases the amplitude of the action potential

• The high resting leak of potassium out of the axon is

minimized

• Less potassium is allowed to leave the axon which

increases the size and duration of the action potential

• Less potassium is allowed to leave the axon which

prevents the inactivation of voltage-gated sodium channels increasing the amplitude of the action potential

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