Chappell M.Payne S.STEPHEN JOHN PAYNE2022-05-242022-05-242020https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085195752&doi=10.1007%2f978-3-030-39705-0_2&partnerID=40&md5=9ef0d8967a14eb763f316bd5f126255dhttps://scholars.lib.ntu.edu.tw/handle/123456789/611725In this chapter we will consider how the cell can maintains its internal environment despite differences in concentration of ions and other charged species both inside and outside of the cell membrane. We outline the principles of concentration balance, electrical neutrality and Gibbs-Donnan equilibrium and how to apply them to a model of a cell. We then see how to calculate equilibrium potentials for individual ions as well as the membrane potential and understand why these are not always the same value. ? 2020, Springer Nature Switzerland AG.[SDGs]SDG2book part10.1007/978-3-030-39705-0_22-s2.0-85085195752