Some Simple Types of Organic Molecules

and their functional groups


Organic molecules with a hydroxyl group (-OH).

Methanol [CH3OH] and ethanol (beverage alcohol)[CH3CH2OH] are common examples.

Sugars are also alcohols.

Carboxylic Acids

Contain one or more carboxyl groups [-COOH].

Many of the intermediates in the breakdown of foodstuffs by cellular respiration are carboxylic acids. [Link]


Contain a carbon atom to which is attached one hydrogen atom and — by a double bond — one oxygen atom.

Formaldehyde [HCHO] is a powerful disinfectant and preservative (it denatures proteins).

Acetaldehyde is produced during the conversion of pyruvic acid to ethanol when yeast ferment sugars [Link]. The converse is also true — acetaldehyde is produced in the liver as it metabolizes ingested ethanol (and may be the prime culprit in a "hangover").

Phosphoglyceraldehyde is an intermediate in glycolysis and the "dark reactions" of photosynthesis.


Formed when two carbon atoms are linked by an oxygen atom.

Diethyl ether is a commonly-used anesthetic. [Link]


The removal of a molecule of water between the -OH group of an alcohol and the -OH group of a produces an ester.


Organic molecules with a carbonyl group (-C=O) between two hydrocarbon portions.

Ketones are synthesized in the liver, usually from fatty acids.

When glucose metabolism is suppressed, during starvation or in diabetics, fatty acids are used as a source of energy. But instead of entering the citric acid cycle, the acetyl-CoA produced from them is converted into the ketone acetoacetate. Some of this is then converted into acetone (which can be smelled on the breath of patients whose diabetes is out of control).


Organic molecules with an amino group, -NH2. Some examples:


Amides are organic molecules containing a carbonyl group (-C=O) attached to a nitrogen atom. The peptide bond between the amino acids linked in a polypeptide is also called an amide bond.

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27 February 2011