Monomers & Polymers as Biological Molecules (College Board AP Biology)

Polymers and Monomers in Biological Systems

• Polymers play an important role in biological molecules
• The term 'biological macromolecule' is often used to describe biological polymers
• A polymer is made of a large number of monomers joined together
• Many metabolic processes involve the breaking and making of biological macromolecules

Dehydration Synthesis

• Is the process by which two molecules of monomer join together with a covalent bond
  • A molecule of water is given off as a byproduct
    • Hence the term 'dehydration'
  • This water molecule joins the cell cytosol and forms part of the cell's normal water content
• Two monomers joined together are called a dimer, 3 monomers is a trimer etc.
• Many monomers joined together form a polymer
• One large molecule is produced (synthesized)
• When this happens many times over, a polymer begins to form, with the production of a water molecule each time a new monomer joins the polymer
• This is a common theme in the building of many different types of biological macromolecules
• Dehydration synthesis is sometimes referred to as condensation

Biological polymers table

Monomer	Polymer
Monosaccharide (eg, glucose)	Starch, glycogen, cellulose
Amino acids	Polypeptides and proteins
Nucleic acids	Nucleotides

The basis of dehydration synthesis diagram

Written and symbolic illustrations of the removal of water to form a covalent bond between 2 or more monomers during a dehydration synthesis reaction

Hydrolysis

• Hydrolysis means ‘lyze’ (to break) and ‘hydro’ (with water)
• In the hydrolysis of polymers, covalent bonds are broken when water is added

Written and symbolic illustrations of the addition of water to break down covalent bond/s during a hydrolysis reaction

Summary table of the covalent bonds formed by dehydration synthesis and broken by hydrolysis