Biomolecules, also known as biological molecules or macromolecules, are organic molecules that are essential for various biological processes and functions within living organisms. These molecules are the building blocks of life and play crucial roles in the structure, function, and regulation of cells and living systems. Biomolecules are primarily composed of carbon, hydrogen, oxygen, nitrogen, and, in some cases, sulfur and phosphorus.

There are four major classes of biomolecules:

1. Proteins: Proteins are large, complex molecules composed of amino acids linked together by peptide bonds. They serve a wide range of functions in living organisms, including enzyme catalysis, structural support, immune response, and transportation of molecules.

2. Nucleic Acids: Nucleic acids, including DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are responsible for the storage and transmission of genetic information. DNA contains the genetic instructions necessary for the development, functioning, and reproduction of organisms, while RNA plays a key role in protein synthesis.

3. Carbohydrates: Carbohydrates are organic compounds made up of carbon, hydrogen, and oxygen atoms. They serve as a primary source of energy for cells and play roles in energy storage (e.g., glycogen and starch) and structural support (e.g., cellulose in plant cell walls).

4. Lipids: Lipids are a diverse group of hydrophobic molecules, including fats, phospholipids, and steroids. They are involved in energy storage, insulation, cellular membrane structure, and signaling processes. Fats, for example, are a concentrated form of energy storage in the body.