Which ion has the highest intracellular concentration in most animal cells?
Intracellular ion composition is highly asymmetric relative to extracellular fluid actively maintained using ATP to support excitability volume and enzyme function. In most mammalian cells at rest dominant intracellular cation is potassium one thirty to one forty millimolar inside versus four to five outside ten to thirtyfold gradient while sodium inverse ten to fifteen inside versus one forty five outside chloride four to twenty inside versus one ten outside bicarbonate ten inside versus twenty five outside free calcium extremely low one hundred nanomolar inside versus one point two millimola
Ref: Lodish et al., Molecular Cell Biology, 8th ed., Chapter 11: Intracellular Ion Composition – High K+.
