1. Out of the following, which is not a major intracellular electrolyte? - GMCH Chandigarh - 2022

GMCH Chandigarh - 2022

Applied Physiology

Easy

Appeared in: GMCH Chandigarh - 2022

Explanation

Sodium (Na⁺) is the primary cation in the extracellular fluid (ECF), the fluid outside the cells.
Its concentration is much lower inside the cell compared to outside, making it a minor intracellular electrolyte.
The sodium-potassium pump actively transports sodium out of cells to maintain this concentration gradient, which is essential for nerve impulses and muscle function.
Therefore, sodium is not considered a major intracellular electrolyte.

Option B: Potassium (K⁺) is incorrect because it is the most abundant and primary cation within the intracellular fluid (ICF).
Option C: Magnesium (Mg²⁺) is incorrect because it is the second most abundant cation within the intracellular fluid.
Option D: Phosphorous/Phosphate (PO₄³⁻) is incorrect because it is the primary anion within the intracellular fluid.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Intracellular vs. Extracellular Electrolytes as background academic context rather than a clinical decision trigger.
Understanding the difference between intracellular and extracellular electrolytes is fundamental for a nurse to interpret lab results and manage fluid and electrolyte imbalances.
For example, a patient with hypernatremia (high sodium) has an excess of an extracellular electrolyte, leading to fluid shifts out of the cells and causing cellular dehydration. A nurse would monitor for neurological changes like confusion or seizures.
Conversely, a patient with hyperkalemia (high potassium) has an excess of an intracellular electrolyte in the blood, which can cause life-threatening cardiac dysrhythmias. The nurse's priority is to monitor the patient's cardiac rhythm.

How to Approach the Question

First, identify the key terms in the question: "not" and "major intracellular electrolyte". The word "not" indicates you are looking for the exception among the options.
Recall the basic physiology of fluid compartments. The body has two main compartments: intracellular (inside cells) and extracellular (outside cells).
Remember the primary electrolytes for each compartment. A simple mnemonic is "Salt (Sodium) is outside the party, but Potassium is the life of the party inside."
Evaluate each option: Is Potassium (K⁺) a major intracellular electrolyte? Yes. Is Magnesium (Mg²⁺)? Yes. Is Phosphate (PO₄³⁻)? Yes.
Evaluate Sodium (Na⁺). Is it a major intracellular electrolyte? No, it's the major extracellular electrolyte.
Select Sodium as the answer because it is the one that does not fit the description of a major intracellular electrolyte.

Concept Tested & Keywords

Concept Tested: Intracellular vs. Extracellular Electrolytes
Stem keywords: intracellular electrolyte
Lead-in keywords: not
Negative lead-in flag: Question asks for the exception (NOT a major intracellular electrolyte).

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