The element phosphorus performs several key roles in modern-day biochemistry. These include acting as a store of chemical energy in phosphate anhydride bonds such as ATP, linking together nucleosides as part of DNA and RNA, and separating cells from the outside environment as phospholipid membranes. Phosphorus is critical to these roles broadly due to capacity for a triple negative charge at high pH. At physiological pH, the charge on phosphate is typically -1 or -2, and the spare hydroxy group(s) may link to one or two organic compounds, forming a molecule with a net negative charge. This negative charge helps to ensure molecular stability in water by fending off hydrolysis of key bonds, increases solubility and inhibits diffusion, and provides a recognition element for binding as a molecular substrate to enzymes.

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