A biomolecule, also known as a biological molecule, is any of the countless substances created by cells and living organisms. Biomolecules come in a variety of shapes and structures, and they serve a broad spectrum of purposes. Carbohydrates, lipids, nucleic acids, and proteins are the four main kinds of biomolecules.Nucleic acids, specifically DNA and RNA, are biomolecules that have the unique function of preserving an organism's genetic code—the sequence of nucleotides that decides the amino acid sequence of proteins, which are essential to living on Earth. There are 20 different amino acids that can appear within a protein, and the sequence in which they occur is critical to protein structure and function. Proteins are important building components of organisms. They also function as transporters, transporting nutrients and other molecules into and out of cells, as well as enzymes and catalysts for the overwhelming majority of chemical processes that occur in living creatures. Proteins can also be used to make antibodies and hormones, and they can affect gene function.Carbohydrates, which are mainly made up of molecules containing carbon, hydrogen, and oxygen atoms, are important energy sources and structural components of all living and are among the most common biomolecules on Earth. They're made up of four different kinds of sugar units: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Lipids, another important biomolecule in living creatures, serve a variety of functions, including energy storage and chemical mediators. They also create membranes, which divide cells from their environments and compartmentalize the cell interior, giving birth to organelles in higher (more complicated) organisms such as the nucleus and the mitochondrion.
All biomolecules share a basic connection between structure and function, which is affected by variables such as the environment in which they appear. Lipids, for example, are hydrophobic ("fearful of water"); in water, many naturally organize themselves so that the hydrophobic ends of the molecules are shielded while the hydrophilic ends are exposed. Lipid bilayers, or two layers of phospholipid molecules, create the walls of cells and organelles as a result of this configuration.