USABO Open Exam ACTUAL

USABO Open Exam (ACTUAL -) | 100% Correct Answers | Verified |

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Which of the following ions have higher extracellular concentrations than intracellular concentrations?

• Potassium

II. Sodium III. Calcium

• I only
• II only
• I and II
• I, II, and III
• II and III - <<>>E. II and III

Select the statement that best describes movement of O2 , Na+ , and glucose into and out of the capillaries.

• O2 and glucose diffuse across endothelial cell membranes;

Na+ diffuses through pores between cells.

• O2 and Na+ diffuse across endothelial cell membranes;

glucose diffuses through pores between cells.

• O2 diffuses across endothelial cell membranes; Na+ and

glucose diffuse through pores between cells.

• O2 , Na+, and glucose all diffuse across endothelial cell

membranes.

• O2 , Na+ , and glucose all diffuse through pores between

endothelial cells. - <<>>C. O2 diffuses across 2 / 3

endothelial cell membranes; Na+ and glucose diffuse through pores between cells.

A new chemical is found that inhibits muscle function and in high enough doses causes paralysis. Which of the following is NOT a plausible mechanism by which this chemical could function?

• Inhibition of acetylcholinesterase in the synaptic cleft of

peripheral motor neurons.

• Inhibition of acetylcholine release in peripheral motor

neurons.

• Inhibition of calcium release in peripheral motor neurons.
• Inhibition of the binding of myosin heads to actin filaments

in muscle cells.

• Inhibition of calcium-release channels in the sarcoplasmic

reticulum of muscle cells. - <<>>C. Inhibition of calcium release in peripheral motor neurons.

A dog breeder wants to breed dogs with thick, shaggy coats.Assume that the thick-coat trait is recessive. Two dogs, both with thick coats and of the same breed, are mated, but all the puppies are short-haired. From this you can conclude that...

• Having two copies of the thick coat allele is lethal.
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