Where are sodium ions predominantly found in the body?

• A. In the mitochondria
• B. Outside the cell
• C. Inside the cell
• D. In the nucleus

Answer: (B)

Verified step by step guidance

1. Understand the distribution of sodium ions in the body: Sodium ions (Na+) are crucial for various physiological processes, including nerve impulse transmission and muscle contraction.
2. Recognize the role of the cell membrane: The cell membrane maintains a concentration gradient of sodium ions, which is essential for cellular functions.
3. Identify the location of sodium ions: Sodium ions are predominantly found outside the cell, in the extracellular fluid, due to the action of the sodium-potassium pump.
4. Consider the sodium-potassium pump: This pump actively transports sodium ions out of the cell and potassium ions into the cell, maintaining a high concentration of sodium ions outside the cell.
5. Conclude the distribution: Given the function of the sodium-potassium pump and the concentration gradient, sodium ions are primarily located outside the cell in the extracellular space.