The chemical compounds of living things are known as organic compounds because of their association with organisms and because they are carbon-containing compounds. Organic compounds, which are the compounds associated with life processes, are the subject matter of organic chemistry. Among the numerous types of organic compounds, four major categories are found in all living things: carbohydrates, lipids, proteins, and nucleic acids.

“The theory of vitalism applies to the properties of organic compounds”, which states that there is a life force present in organic compounds that are essential to living things, and this force is not present in non-living (and therefore, inorganic) things.

Organic compounds contain  functional groups, a structural unit made up of groups of atoms in a molecule that are bonded to the rest of the molecule by a covalent bond; this bond forms between the functional group and a carbon atom from the main body of the molecule.

Size is another property of organic compounds that offers great variation from one compound to the next.Organic compounds-specifically ones that are important to different fields of biology-often contain long chains of carbon atoms which can loop around each other; different atoms can form bonds with these carbons, creating variation in the molecule and its functional groups.

Solids are known to be organic compounds that have a defined shape and volume. Liquids have a less defined shape and volume, whereas gases have an indefinite shape. The higher the melting/boiling point, stronger the intermolecular force for a given compound.An interamolecular force is the attraction or repulsion that is displayed between atoms.