Proteins, carbohydrates, nucleic acids, and lipids are the four major classes of biological macromolecules—large molecules necessary for life that are built from smaller organic molecules. Macromolecules are comprised of single units scientists call monomers that are joined by covalent bonds to form larger polymers.

When polymers break down into smaller units (monomers), they use a water molecule for each bond broken by these reactions. The polymer is more than the sum of its parts: it acquires new characteristics, and leads to an osmotic pressure that is much lower than that formed by its ingredients.

biological macromolecule — large molecule necessary for life that is built from smaller organic molecules. carbohydrate — biological macromolecule in which the ratio of carbon to hydrogen and to oxygen is 1:2:1; carbohydrates serve as energy sources and structural support in cells and form…. polymer — chain of monomer residues that covalent bonds link; polymerization is the process of polymer formation from monomers by condensation. lipid — macromolecule that is nonpolar and insoluble in water.