Question

Negatively charged ions are required to balance the net positive charge from metal ions such as K+, Na+, and Ca2+. Which of the following negatively charged ions is the most abundant outside the cell and which ion does most often neutralize (written in parentheses)?

(a) Cl- (Ca2+)
(b) PO43- (K+)
(c) PO43- (Ca2+)
(d) Cl- (Na+)

Answer 1

The most abundant negatively charged ion outside the cell is chloride (Cl-), and it most often neutralizes sodium (Na+) ions, as indicated by option (d) Cl- (Na+).

Step-by-step explanation:

The most abundant negatively charged ion outside the cell is chloride (Cl-), and it most often neutralizes sodium (Na+) ions. To maintain charge balance and the resting membrane potential, these ions move across the cell membrane. The sodium-potassium pump actively transports three Na+ ions out of the cell for every two K+ ions pumped in, contributing to a net positive charge outside the cell and a net negative charge inside the cell. The chloride ions (Cl-) are abundant in the extracellular fluid (ECF) because they balance the positive charge of Na+, which is present in high concentrations outside the cell.

In conclusion, the correct answer to which negatively charged ion is most abundant outside the cell and which ion it most often neutralizes when written in parentheses is (d) Cl- (Na+).