Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell.Which of the following ions is the most abundant inside a typical mammalian cell?

Ion channels are classified as membrane transport proteins.They discriminate between ions based on size and charge.In addition to Na⁺, which one of the following ions would you expect to be able to freely diffuse through a Na⁺ channel? Explain your answer.

Which of the following channels would not be expected to generate a change in voltage by movement of its substrate across the membrane where it is found?