Function and Metabolism of Phosphorus


Phosphorus accounts for about 1% of body weight or one fourth of the total mineral matter in the body. About 85% of the phosphorus is in an inorganic combination with calcium as the the insoluble salt of bones and teeth. In bones, the proportion of calcium to phosphorus is about 2 to 1. But soft tissues contain much higher amounts of phosphorus than calcium. Most of this phosphorus is in an organic combination. Phosphorus is used in a variety of different functions in our body.

Function of Phosphorus:

1. Phosphorus is a constituent of the sugar phosphate linkage in the structures of DNA and RNA, which control heredity.

2. Phospholipids are constituents of cell membranes and regulate the transport of solutes into and out of the cell.

3. The Phosphorus containing lip-proteins facilitate the transport of the fats in the circulation.

4. Phosphorylation is a key reaction in a number of metabolic processes. For example, the the Phosphorylation of glucose for absorption from the intestines, the uptake of glucose by the renal tubules. Similarly, monosaccharides are Phosphorylated in the initial stages of metabolism to yield energy.

5. Phosphorus compounds are essential for the storage and controlled release of energy – the ADP-ATP system in the niacin containing coenzyme requited for oxidation – reduction reactions – NADP NADPH and for the active form of thiamine for de-carboxylation reactions – TTP.

Metabolism of Phosphorus:

Much of the phosphorus in foods is in organic combination that are split by intestinal phosphates to free the phosphate. The Phosphorus is absorbed as inorganic salt. About 70% of dietary Phosphorus is normally absorbed.

The inorganic Phosphorus content of blood serum ranges from 2.5 to 4.5 mg/dl. It is slightly higher in children. The level is kept constant through regulation by the kidneys. All of the plasma inorganic phosphate is filtered through the renal glomeruli and most of it is reabsorbed. Vitamin D increases the rate of re-absorption by the tubules and parathyroid hormone decreases the re-absorption.