1 A) numerous open sodium channels; more than for any other ion. B) many open sodium channels. C) very few open sodium channels. 2 A) sodium ions rush into the cell, down the concentration gradient. B) sodium ions rush out of the cell, down the concentration gradient. C) sodium ions may enter the cell, but are pumped out by the Na/K-ATPase pump. D) sodium ions may leave the cell, but are pumped back in by the Na/K-ATPase pump. 3 A) water leaves the cell, and the cell swells. B) water leaves the cell, and the cell shrinks. C) water enters the cell, and the cell swells. D) water enters the cell, and the cell shrinks. 4 A) 200 to 240 mM. B) 120 to 160 mM. C) 0 to 200 mM. 5 A) When a red blood cell is placed in hypotonic (very dilute) solutions of NaCl: B) water leaves the cell, and the cell swells. C) water enters the cell, and the cell shrinks. D) water enters the cell, and the cell swells. 6 A) sodium ions rush into the cell, down the concentration gradient. B) sodium ions rush out of the cell, down the concentration gradient. C) some sodium ions may leave the cell. D) some sodium ions may enter the cell. 7 A) 0 to 120 mM. B) 150 to 180 mM. C) 200 to 250 mM. 8 A) water enters the cell, and the cell swells and bursts. B) water neither leaves nor enters the cell; the cell neither swells nor shrinks. C) water leaves the cell, and the cell shrinks. 9 A) between 0 and 100 mM. B) between 140 and 180 mM. C) between 200 and 240 mM. 10 A) water entered the cell, and the cell swelled and burst. B) water neither left nor entered the cell; the cell neither swelled nor shrank. C) water left the cell, and the cell shrank.
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