How is potassium distributed between human cells and blood plasma?
![A periodic table element box for potassium shows atomic number 19, symbol K, atomic weight 39.0983, electron configuration [Ar]4s1, and name potassium. Icons indicate it is an alkali metal, solid at room temperature, body-centered cubic crystal structure, and has strongly basic higher-valence oxides. A key explains the symbols for alkali metals, solid state, body-centered cubic structure, and strong basicity.](https://cdn.britannica.com/81/22381-050-E3372C94/properties-Potassium.jpg)
Potassium is the primary inorganic cation found within living cells, while sodium is the most abundant cation in extracellular fluids, such as blood plasma. The distribution of potassium between these two environments is tightly regulated to maintain essential physiological functions, including the transmission of electrochemical impulses in nerve and muscle fibers.12
In humans, the ratio of potassium concentration between the cell and blood plasma is approximately 27:1. Specifically, the potassium content of muscle tissue is about 0.3 percent, whereas the concentration in blood serum is significantly lower, at approximately 0.01–0.02 percent.1
This concentration gradient is maintained by the sodium-potassium pump, a protein located in the cell membrane that uses metabolic energy to actively transport potassium ions into the cell and sodium ions outward. Because precise potassium levels are vital for survival, the body regulates its balance through dietary intake and renal excretion, with the kidneys adjusting the amount of potassium secreted into urine based on physiological needs.231