• All living things are made up of four classes of 
large biological molecules: carbohydrates, lipids, 
proteins, and nucleic acids
• Macromolecules are large molecules composed 
of thousands of covalently connected atoms
• Molecular structure and function are inseparableMacromolecules are polymers, built from 
monomers
• A polymer is a long molecule consisting of many 
similar building blocks 
• These small building-block molecules are called 
monomers
• Three of the four classes of life’s organic molecules 
are polymers
– Carbohydrates
– Proteins
– Nucleic acids