TuviaDaCat said:im asking this because chemically they are very similar, and the only big difference i see is that potassium is much larger.
i got the details for mammalian cell typical ion concentrations and it is such:
inside outside (mM)
K+ 5-15 145
Na+ 140 5
so what does the cell has against Na?
TuviaDaCat said:if we wanted a nice gradient then taking Na out would do, but it takes in K+
K+ is a weak ion but more mobile than Na+.The different characteristics of the intracellular and extracellular environments manifest themselves particularly in terms of restricted diffusion and a high concentration of chaotropic inorganic ions and kosmotropic other solutes within the cells. Note that both chaotropic inorganic ions and kosmotropic other solutes encourage low density water structuring. The difference in concentration of the ions is particularly apparent between Na+ and K+ (see below); Na+ ions creating more broken hydrogen bonding and preferring a high aqueous density whereas K+ ions prefer a low density aqueous environment. A 1000-fold preference for K+ over Na+ has been found in a halophilic organism without any energy expenditure but with a highly reduced intracellular water mobility [817]. As explained in discussion of the Hofmeister effect and shown by the negative apparent ionic volumes (that is, addition of the ions reduces the volume of the water, see below), the interactions between water and Na+ are stronger than those between water molecules, which in turn are stronger than those between water and K+ ions; all being explained by the differences in surface charge density. The interaction strength is reflected in that the distance between the Na+ ions and water is shorter than between two water molecules which is shorter than between K+ ions and water. Ca2+ ions have even stronger destructive effects, on the hydrogen bonding, than Na+ ions. Clearly, K+ ions are preferred within the intracellular environment.
Cells prefer potassium over sodium because K+ is the major positively charged ion inside the cell, while Na+ is the major positively charged ion outside the cell. This creates an electrical gradient that drives K+ into the cell and keeps Na+ out, maintaining the cell's overall negative charge.
The cell maintains a higher concentration of K+ compared to Na+ through the action of sodium-potassium pumps, which actively transport K+ into the cell and Na+ out of the cell against their concentration gradients.
K+ plays a crucial role in many cellular processes, including maintaining cell volume and osmotic balance, regulating enzyme activity, and participating in the transmission of nerve signals.
No, cells cannot function without K+. K+ is essential for maintaining the proper electrical balance and functioning of cells. While Na+ can play a role in some cellular processes, it cannot fully substitute for the functions of K+.
If there is an imbalance of K+ and Na+ in the cell, it can disrupt the cell's normal functions and lead to various health problems. For example, a high concentration of K+ inside the cell can cause abnormal heart rhythms, while a low concentration of K+ can result in muscle weakness and cramps.