What is the function of phosphorus?

WCL Staff Nurse - 2022

Applied Physiology

Easy

Appeared in: WCL Staff Nurse - 2022

Explanation

the development of bones and teeth.
Phosphorus is a critical mineral that combines with calcium to form calcium phosphate, also known as hydroxyapatite.
This compound is the primary structural component that provides hardness and rigidity to bones and teeth.
Approximately 80-85% of the total phosphorus in the adult body is found in the skeleton and teeth, highlighting this as its most significant quantitative role.

Option B: While phosphorus is a component of the phosphate buffer system and does help regulate pH, this is not its most significant or primary function compared to its structural role in bones. The bicarbonate buffer system is the main regulator of extracellular fluid pH.
Option C: The direct trigger and regulation of muscle contraction depend on the release and binding of calcium ions (Ca²⁺). Phosphorus's role is indirect, providing the energy for contraction in the form of ATP.
Option D: The propagation of a nerve impulse (action potential) is primarily governed by the rapid influx of sodium (Na⁺) and efflux of potassium (K⁺) ions across the nerve cell membrane. Phosphorus is involved indirectly via ATP for energy and as a component of the cell membrane's phospholipids.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Physiological functions of phosphorus as background academic context rather than a clinical decision trigger.
Nurses frequently manage patients with phosphorus imbalances (hypophosphatemia and hyperphosphatemia), especially those with chronic kidney disease (CKD).
In CKD, the kidneys fail to excrete phosphorus, leading to hyperphosphatemia. This can cause severe itching (pruritus), bone and joint pain, and increase the risk of cardiovascular events. Nursing care involves administering phosphate binders with meals and educating patients on low-phosphorus diets.
Hypophosphatemia can cause muscle weakness (including respiratory muscle weakness), altered mental status, and bone pain. It is often seen in refeeding syndrome, alcoholism, and with certain medications.

How to Approach the Question

First, identify the keyword in the question, which is "phosphorus".
The question asks for its "function". This requires recalling the major physiological roles of this mineral.
Evaluate each option. Think about which function is the most significant or primary role of phosphorus.
Recall that about 85% of the body's phosphorus is stored in bones and teeth, making this its largest quantitative role.
Consider the other options. While phosphorus is involved in pH, muscle, and nerve function, other minerals (calcium, sodium, potassium) play a more direct regulatory role in those processes.
Select the option that represents the most prominent and direct function of phosphorus, which is its structural role in bones and teeth.

Concept Tested & Keywords

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E6 Biochemistry U Satyanarayana— Part 2 (pp 421-820 of 840) p. 26-28

E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 551-553