aldehyde
Meaning of aldehyde: The reactive group that pickles tissue for the microscope, sterilizes instruments, and forms as the toxic middle step of alcohol breakdown.
Definition of aldehyde
An aldehyde is any compound holding a carbon atom double bonded to oxygen with a hydrogen attached to that same carbon. The arrangement sits at the end of a chain and is chemically reactive, attacking proteins and DNA readily. Oxidizing a simple alcohol produces one, and oxidizing it a step further produces an acid. Formaldehyde and acetaldehyde are the members that matter most in medicine.
Why are they so reactive?
The oxygen pulls electrons away from the carbon it is bonded to, leaving that carbon short of them and eager to react with anything electron-rich nearby. Proteins and DNA are full of such groups. An aldehyde meeting a protein forms a permanent bond, and a molecule with an aldehyde group at each end can bridge two proteins together. That single property explains almost every use and every hazard the group has: it locks tissue in place, it kills organisms by cross-linking their proteins, and it damages genetic material.
Which ones matter in medicine?
| Aldehyde | Where it is met | Concern |
|---|---|---|
| Formaldehyde | Fixing tissue samples, embalming | Irritant; classified as causing cancer in humans |
| Glutaraldehyde | Cold sterilization of endoscopes | Occupational asthma and skin reactions |
| Acetaldehyde | Made in the body from alcohol | Flushing, nausea, damage to DNA |
| Retinal | A form of vitamin A in the retina | None; it is essential for vision |
That last row matters for the definition. An aldehyde is a chemical arrangement, not a class of poison, and the same group sits inside a vitamin the eye cannot work without.
Why does drinking produce a toxic intermediate?
Breaking down alcohol takes two steps. One enzyme converts it to acetaldehyde, and a second converts the acetaldehyde to acetate, which the body handles easily. The intermediate is far more toxic than either the drink or the end product, and it is responsible for much of the nausea and headache that follow heavy intake. An inherited variant common across parts of East Asia leaves the second enzyme sluggish, so acetaldehyde accumulates and produces immediate facial flushing, along with a raised risk of esophageal cancer where drinking continues. One medicine used in alcohol dependence blocks that second enzyme deliberately, creating the same unpleasant reaction on purpose.
Used in a sentence
The specimen was fixed in an aldehyde solution before sectioning.
Good to know
Acetaldehyde is the intermediate formed as the body breaks down alcohol, and an inherited variant that slows its removal produces facial flushing after drinking together with a higher risk of cancer of the esophagus.
Word origin
Where “aldehyde” comes from
The name is a contraction of the Latin phrase alcohol dehydrogenatum, meaning alcohol with its hydrogen removed, which describes how the group is produced from an alcohol.