Components of Organic Molecules


Carbon atoms are the backbone of organic molecules. The molecule may have a solitary carbon atom or many carbon atoms arranged in various configurations. Hydrogen, oxygen and nitrogen join the carbon skeleton to complete the molecule, and elements such as phosphorus, sulfur, iron and magnesium make an occasional appearance. The manner in which these elements join together is not haphazard. Each molecule is composed of distinct components organized in an orderly fashion to form a unified whole.

Carbon Chains

  • A carbon chain is a row of carbon atoms joined to one another. The compound octane has eight carbon atoms lined up in a row. In addition to the principal chain, there may be side chains in which another row of carbon atoms branch off from the main chain.


  • Some organic molecules possess a component called a ring. This ring occurs when three or more carbon atoms join together in such a way that they form a circle. A benzene ring has six carbon atoms joined together in this way. If the ring includes one or more nitrogen or oxygen atoms in addition to the carbon, the ring is called a heterocyclic ring.

Carboxyl Group

  • The carboxyl group is a component of organic acids. Its formula is --COOH, where the hyphen marks the point at which this component is attached to the rest of the molecule. A carbon atom has four places where it can attach itself to other molecules: four hands, as it were. In the carboxyl group, the carbon atom uses two hands to hold on to one oxygen atom, one hand to hold on to the other oxygen atom (to which the hydrogen atom is attached), and one hand to hold on to the rest of the organic molecule.

Hydroxyl Group

  • The formula for the hydroxyl group is --OH. It is a component of alcohols. Whereas the carbon atom has four hands, the oxygen atom has only two. In the hydroxyl group, the oxygen atom holds on to the hydrogen atom with one hand; with the other it holds on to the rest of the molecule.

Amino Group

  • The amino group has the formula --NH2. This group is a component of organic molecules called amino acids, amines and amides. Nitrogen has three hands. One hand attaches itself to the rest of the molecule while each of the other two hands grab a hydrogen atom.

Carbonyl Group

  • The carbonyl group consists of a carbon atom holding on to an oxygen atom with two of its hands. With its other two hands that are still free, the carbon atom holds on to the rest of the molecule. In a compound called a ketone, each of the two free hands hang on to a different carbon atom of the organic molecule. In a compound called an aldehyde, both free hands attach themselves to the same carbon atom.

Metal Atoms

  • Metal atoms are components of organic molecules called porphyrins. Hemoglobin is a porphyrin with an iron atom at its center. Chlorophyll has magnesium at its center.

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