Biomolecules and Functional Groups

All living organisms are made of biomolecules, which are chemical compounds containing carbon-to-carbon or carbon-to-hydrogen bonds. Carbon is a versatile atom that can bond with hydrogen, oxygen, nitrogen, phosphorus, sulfur, and even itself, forming diverse structures like chains, branched chains, and rings. This ability of carbon is crucial for life.

The carbon chain of a biomolecule is called its skeleton or backbone, analogous to how a human skeleton accounts for shape. The reactivity of a biomolecule is primarily dependent on its functional groups, which are specific groups of bonded atoms that have consistent chemical properties and reactions.

Examples of functional groups include the hydroxyl group, which forms ethanol when attached to a carbon skeleton. In biology, five important functional groups are hydroxyl, carboxyl, amino, sulfhydryl, and phosphate. These groups attach to the carbon skeleton (represented by 'R') and significantly alter the biomolecule's chemical reactivity, thus determining its identity.

For instance, a carboxyl group attached to a carbon backbone forms a fatty acid, while an amino group and a carboxyl group joined to a carbon backbone form an amino acid. All biomolecules are categorized into four classes: proteins, carbohydrates, nucleic acids, and lipids, which will be discussed in further detail in upcoming tutorials.