Cholera is a disease caused by bacteria that make cholera toxin. In the presence of this toxin, chloride ion channels in cells of the small intestine lining are stuck in their open position. As a result, an excess of chloride ions (Cl−) flows from these cells into the lumen of the small intestine. Movement of Cl− creates a charge gradient, so sodium ions (Na+) also flow into the lumen. Explain why the movement of these ions into the lumen results in the life-threatening diarrhea that characterizes cholera.
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