Organic compounds are defined as molecules that have a carbon-hydrogen bond. The compounds have qualities that make them vital to sustaining life. Carbon atoms have properties that allow them to bond to hydrogen and other atoms in a variety of ways, allowing for a combination of molecular arrangements. Organic compounds such as fats, sugars and proteins are all essential for biological functions.
Properties of Carbon
Carbon is an atom that can bond in a variety of ways with other atoms. A molecule of a single carbon atom with a single hydrogen atom is known as a "hydrocarbon." This is the building block of all organic molecules. Carbon's electron shell has certain atomic characteristics that allow the hydrocarbon molecule to arrange itself in different structures, such as a chain, a branched chain, or as a ring of hydrocarbons.
Organic molecules can be formed by biological activity of an organism (such as methane gas emitted by digestive systems of cows) or organic compounds can simply have a carbon base, such as benzene (a compound in petroleum). There are four classes of hydrocarbons. These are differentiated by the type of electron bonding between the carbon atoms. Hydrocarbon molecules may contain carbon atoms that have single bonds (alkanes), double bonds (alkenes), or triple bonds (alkynes). The class of hydrocarbons called "isomers" may have the same chemical formula but can be restructured in different ways. Organic molecules get progressively more complex as other elements, such as nitrogen, sulfur and phosphorus, are included.
Hydrocarbon molecules can form more complex compounds by having "functional groups" attach themselves to the carbon spine of the hydrocarbon. These are other molecules which influence the chemical behavior of the entire organic compound. Functional groups are molecules such as oxygen and hydrogen pairs; these are called "hydroxyls" (also knows as alcohols.) Other functional groups include aminos (nitrogen bonded to two hydrogen atoms) and carbonyls (carbon bonded to oxygen.)
Hydrophilic and Hydrophobic Molecules
The behavior of organic molecules is dependent on how it interacts with water. This is determined by which functional groups attach to the organic molecule's carbon spine. Some molecules may either be hydrophilic (water-soluble like sugars) or hydrophobic (non-soluble in water such as fats.) Certain organic compounds may have parts of the molecule that are hydrophobic and the other parts that are hydrophilic. This is significant for biological functions, as they take place in the presence of water.
Types of Organic Molecules
The most common organic molecules that help sustain life are sugars and starches. Plant life would not be possible without a cellulose, a starch. The building blocks of proteins are organic compounds called amino acids, which are linked together to form complex protein molecules. Other organic compounds are hydrocarbon fossil fuels such as petroleum.