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Summarizing Synthesis of Biological Macromolecules

Summary of lessons so far

Proteins, carbohydrates, nucleic acids, and lipids are the four major classes of biological macromolecules. Biological macromolecules are large molecules necessary for life that are built from smaller organic molecules.

Macromolecules are made up of single units known as monomers that are joined by covalent bonds to form larger polymers. 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. This is an important advantage in the maintenance of cellular osmotic conditions. A monomer joins with another monomer with the release of a water molecule, leading to the formation of a covalent bond. These types of reactions are known as dehydration or condensation reactions.

When polymers are broken down into smaller units (monomers), a molecule of water is used for each bond broken by these reactions. Such reactions are known as hydrolysis reactions.

Dehydration and hydrolysis reactions are similar for all macromolecules, but each monomer and polymer reaction is specific to its class. Dehydration reactions typically require an investment of energy for new bond formation, while hydrolysis reactions typically release energy by breaking bonds.

Glossary of Words

Biological macromolecule

large molecule necessary for life that is built from smaller organic molecules

Dehydration synthesis

(also, condensation) reaction that links monomer molecules together, releasing a molecule of water for each bond formed


reaction causing breakdown of larger molecules into smaller molecules with the utilization of water


smallest unit of larger molecules called polymers


chain of monomer residues that is linked by covalent bonds; polymerization is the process of polymer formation from monomers by condensation

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