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12.3: Phosphorus

  • Page ID
    40995
  • You have already learned about how blood phosphate levels are regulated in the body by PTH, calcitonin, and 1,25(\(\ce{OH}\))2D. Animal products are rich sources of phosphate. Plant products contain phosphorus, but some is in the form of phytic acid (phytate, these names are used interchangeably). In grains, over 80% of the phosphorus is phytate. This structure is shown below1.

    clipboard_eb849d2979a88bb0ff55ba42a41ca3436.png
    Figure \(\PageIndex{1}\): Structure of phytic acid2

    The bioavailability of phosphorus from phytate is poor (~50%) because we lack the enzyme phytase that would cleave the phosphorus so it can be taken up3. Phytate binds to other minerals and decreases our ability to absorb them (you have learned that it is an inhibitor of calcium uptake, you will learn about it binding other minerals in subsequent sections). Nevertheless, ~50-70% of dietary phosphorus is absorbed1. Another source of phosphorus is phosphoric acid that is used to acidify colas. Colas are caramel-colored, carbonated soft drinks that contain caffeine, such as Coca-Cola, Pepsi, etc. Epidemiological studies have found that soft drink consumption is associated with decreased bone mineral densities, particularly in females4,5. It has been hypothesized that phosphoric acid plays some role in this effect, but there is limited evidence to support this belief.

    Most phosphorus is excreted in the urine.

    Phosphorus deficiency is rare, but can hinder bone and teeth development. Other symptoms include muscle weakness, rickets, and bone pain6. Toxicity is also rare, but it causes low blood calcium concentrations and tetany1.

    Query \(\PageIndex{1}\)

    Phosphorus Functions

    Phosphorus has a number of functions in the body1.

    Phosphate is a component of hydroxyapatite in bones and teeth, as described earlier.

    Non-bone functions include:

    Phosphorylation

    Phosphates are used to activate and deactivate a number of proteins. In addition, compounds are also frequently phosphorylated, like the monosaccharides shown below.

    clipboard_e44bb9a0b9cb29adb8089fe1cbc25a562.png
    Figure \(\PageIndex{2}\): Uptake of monosaccharides into the hepatocyte

    Phospholipids

    Phosphates are a component of phospholipids, as shown below.

    clipboard_e9ae489b2d3d57f091f98f80ef6a2ac8b.png
    Figure \(\PageIndex{3}\): Structure of phosphatidylcholine (lecithin)7

    DNA/RNA

    DNA/RNA have a phosphate backbone as shown below.

    clipboard_e25bde544675866692c86d378a79dc05f.png
    Figure \(\PageIndex{4}\): Structure of DNA8

    ATP

    The major energy currency, ATP, stores energy in its phosphate bonds.

    clipboard_e4dacfdf00d60c2ff7b52c6c997a21d5f.png
    Figure \(\PageIndex{5}\): Structure of ATP9

    Other functions of phosphate include:

    • Intracellular secondary messengers cyclic AMP (cAMP) and inositol triphosphate (\(IP_3\)) both contain phosphate
    • Acid/Base Balance
    • Intracellular Anion

    Query \(\PageIndex{2}\)

    References

    1. Gropper SS, Smith JL, Groff JL. (2008) Advanced nutrition and human metabolism. Belmont, CA: Wadsworth Publishing.
    2. en.Wikipedia.org/wiki/File:Phytic_acid.png
    3. Phosphorus. Linus Pauling Institute Micronutrient Information Center. http://lpi.oregonstate.edu/mic/miner...us#reference10
    4. Tucker K, Morita K, Qiao N, Hannan M, Cupples LA, et al. (2006) Colas, but not other carbonated beverages, are associated with low bone mineral density in older women: The framingham osteoporosis study. Am J Clin Nutr 84(4): 936-942.
    5. Libuda L, Alexy U, Remer T, Stehle P, Schoenau E, et al. (2008) Association between long-term consumption of soft drinks and variables of bone modeling and remodeling in a sample of healthy german children and adolescents. Am J Clin Nutr 88(6): 1670-1677.
    6. Byrd-Bredbenner C, Moe G, Beshgetoor D, Berning J. (2009) Wardlaw's perspectives in nutrition. New York, NY: McGraw-Hill.
    7. https://courses.lumenlearning.com/suny-nutrition/chapter/2-36-phospholipids/
    8. https://en.Wikipedia.org/wiki/DNA#/media/File:DNA_chemical_structure.svg
    9. en.Wikipedia.org/wiki/File:ATP_structure.svg

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