Rucete ✏ Campbell Biology In a Nutshell
Unit 1 THE CHEMISTRY OF LIFE — Concept 5.1 Macromolecules are Polymers, Built from Monomers
Life's complexity arises from simplicity: large biological molecules, or macromolecules, are constructed from smaller units called monomers. Understanding this assembly process reveals how diverse functions emerge from basic building blocks.
1. Monomers and Polymers: The Building Blocks of Life
Monomers are simple molecules that serve as the repeating units in polymers. When these monomers link together through covalent bonds, they form polymers, which can be:
Carbohydrates: Sugars and starches
Proteins: Chains of amino acids
Nucleic Acids: DNA and RNA
2. Dehydration Synthesis: Building Polymers
Cells construct polymers through dehydration reactions, where two monomers bond covalently with the loss of a water molecule. This process is facilitated by enzymes and involves:
One monomer providing a hydroxyl group (—OH)
The other providing a hydrogen atom (—H)
This reaction repeats, adding monomers sequentially to elongate the polymer chain.
3. Hydrolysis: Breaking Down Polymers
Conversely, polymers are disassembled into monomers via hydrolysis, a reaction that adds a water molecule to break covalent bonds between monomers. This process is essential in digestion, allowing organisms to:
Break down dietary polymers into absorbable monomers
Reassemble these monomers into new polymers for specific cellular functions
4. Diversity of Polymers: A Limited Set, Infinite Possibilities
Despite the vast array of macromolecules, they are synthesized from a limited set of monomers. For example:
Proteins are composed of 20 different amino acids
DNA and RNA are built from four types of nucleotides
The specific sequence and arrangement of these monomers result in a diverse range of polymers, each with unique properties and functions.
In a Nutshell
Monomers are the fundamental units that, when linked, form polymers.
Dehydration synthesis assembles polymers by removing water molecules.
Hydrolysis breaks down polymers into monomers by adding water.
A limited variety of monomers can create an immense diversity of macromolecules, underpinning the complexity of life.