Potassium concentration is approximately how many times higher inside cells than in extracellular fluid?

• A. 5
• B. 10
• C. 20
• D. 50

Answer: (C)

Potassium is kept at a much higher concentration inside cells than outside, creating a large transmembrane gradient. In most cells, intracellular K+ is about 140 mEq/L and extracellular K+ is around 4 mEq/L, giving roughly a 30–40 fold difference. When rounded for a simple multiple-choice question, saying it is about twenty times higher inside is a reasonable approximation that matches the intended answer. This big gradient is essential for the resting membrane potential; the cell’s Na+/K+ ATPase pump helps maintain it by actively moving K+ into the cell and Na+ out, while K+ leak channels allow some outward movement, shaping the cell's excitability.