Which electrolyte is absorbed in the colon?

Sodium is primarily absorbed in the colon, making it the correct answer. The colon plays a crucial role in the reabsorption of various electrolytes, particularly sodium. As the contents of the intestine move through the digestive tract, water and electrolytes are absorbed, with sodium absorption being a key process that helps maintain fluid and electrolyte balance in the body.

The mechanism of sodium reabsorption in the colon is vital, especially as it helps regulate blood pressure and volume. Special transport proteins, notably sodium-potassium ATPase pumps, assist in actively moving sodium out of the cells lining the colon, allowing it to enter the bloodstream.

In contrast, while calcium, magnesium, and phosphorus are absorbed in the gastrointestinal tract, their primary sites of absorption are in different sections, such as the small intestine rather than the colon. Calcium and magnesium absorption is particularly dependent on vitamin D, and phosphorus is also absorbed in the intestines, contributing to mineral balance but not primarily in the colon.