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Macrominerals Phosphorus

Macrominerals Phosphorus. Dr. Sherin Bakhashab. Phosphorus. Sources: Milk and milk products (the richest sources) Fish, meat, liver and kidney Leafy vegetables and egg yolk Requirements: Adult men and women: 800 mg/ day Children, pregnant and lactating women: 800 – 1200 mg/day

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Macrominerals Phosphorus

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  1. MacromineralsPhosphorus Dr. Sherin Bakhashab

  2. Phosphorus • Sources: • Milk and milk products (the richest sources) • Fish, meat, liver and kidney • Leafy vegetables and egg yolk Requirements: • Adult men and women: 800 mg/ day • Children, pregnant and lactating women: 800 – 1200 mg/day Excretion: Mostly 90% is excreted in urine.

  3. Absorption • Phosphorus (in the form of phosphate) is absorbed by an active transport mechanism in the mid jejunum and enters blood stream via portal circulation. • Absorption is regulated by active vitamin D (calcitriol). • Factors affecting Ca absorption will affect phosphorus absorption in the same manner.

  4. Body Phosphorus • Total body phosphorus is about 800 g. • Most of the phosphorus (80%) is present in the skeleton (bones and teeth). • The other 20% is present in other tissues (mostly intracellular) and body fluids.

  5. Blood Phosphorus • Normal plasma inorganic phosphorus between 3-5 mg/dl. • Other forms are present: • In plasma: phospholipids • In red blood cells (RBCs): organic phosphate, e.g. ATP, glucose-6-phosphate.

  6. Factors Affecting Blood Phosphorus • Parathyroid hormone: Decreases phosphorus by stimulating its excretion through inhibiting the renal tubular reabsorption of phosphate. • Active vitamin D (calcitriol) • Hypophosphataemia stimulates directly the renal hydroxylation of 25(OH)D3. • Calcitriol increases blood phosphorus through stimulation of: • Absorption of phosphorus from the intestine. • Bone resorption, i.e., mobilization of phosphorus from bones. • Renal reabsorption by renal tubules.

  7. Factors Affecting Blood Calcium and Phosphorus

  8. Functions of Phosphorus • It comprises the structure of bones and teeth. • It enters in the structure of the following cellular components: • Nucleic acids: DNA, RNAs. • Phospholipids: e.g. lecithin, cephalin. • Phosphoproteins • Coenzymes: e.g. NAD, NADP. • High energy phosphate compounds: e.g. ATP, GTP, creatine phosphate. • Cyclic AMP, GMP • Carbohydrate intermediates: e.g. glucose-6-phosphate, fructose-1-phosphate.

  9. Functions of Phosphorus • It enters in the formation of blood buffers. Phosphate buffer system: dihydrogen phosphate (H2PO4-) and monohydrogen phosphate (HPO42-) are the ions used in this system. H2PO4- acts as a weak acid:

  10. Phosphate buffer system • HPO4- acts as a weak base: • H+ + HPO42- H2PO4- • Hydrogen ion • (strong acid) Monohydrogen Phosphate (weak base) Dihydrogen Phosphate (weak acid)

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