phosphoric acid
Meaning of phosphoric acid: The tartness in a cola, the etching gel at a dental appointment, and part of the backbone holding every DNA strand together.
Definition of phosphoric acid
Phosphoric acid is a mineral acid made of phosphorus, oxygen and hydrogen, supplied as a colorless syrupy liquid or as a dilute solution. It flavors cola drinks, etches tooth enamel so that a filling will bond to it, and strips rust from steel. Units derived from it link the backbone of DNA and RNA and carry the stored energy in ATP.
Where is it used?
| Setting | What it does there |
|---|---|
| Soft drinks | Supplies the sharp taste of cola |
| Dentistry | Roughens enamel so a filling or sealant grips |
| Metalwork | Converts rust into a stable coating |
| Fertilizer industry | Starting material for phosphate fertilizers |
| Laboratory | Holds a solution at a steady acidity as a buffer |
Is it the same thing as phosphate?
They are two forms of the same chemistry. Phosphoric acid carries three hydrogen atoms that it can release. As each one leaves, what remains is a negatively charged phosphate ion. In body fluids, which are close to neutral, almost all of it exists in those ionized forms rather than as the free acid. So the acid on a laboratory shelf and the phosphate in blood are chemically related, and the words are often used loosely as if interchangeable.
What is its role in the body?
Phosphate groups are everywhere in biology. Alternating sugar and phosphate units form the two rails of the DNA ladder, which is why nucleic acids are acidic at all. ATP, the molecule cells spend as currency, stores its energy in the bonds between three phosphate groups in a row. Attaching or removing a phosphate group is also the commonest way a cell switches a protein on or off. Most of the body's phosphorus sits in bone and teeth, locked with calcium into the mineral that gives them their hardness, and the kidneys govern how much is kept and how much is passed out.
Does the acid in soft drinks affect teeth?
Acid of any kind softens the mineral surface of enamel, and repeated exposure over time contributes to erosion. The effect depends on how often and how long the acid contacts the teeth rather than on the total amount drunk. Sugar-free colas contain the same acid, so removing the sugar does not remove that particular effect.
Also known as
Used in a sentence
The bonding protocol called for the enamel surface to be conditioned with phosphoric acid before placement.
Good to know
Phosphoric acid and phosphate describe the same chemistry in different states of ionization, so the words are frequently exchanged in general writing.
Word origin
Where “phosphoric acid” comes from
Phosphorus comes from the Greek phosphoros, meaning light bearer, a name given to the element because a form of it glows in air.