Polymers are large molecules composed of repeating subunits called monomers. Imagine building a chain with individual links – each link is like a monomer, and together they form the long chain of the polymer.
Here's how they're built:
1. Monomer Activation:
- Monomers are small molecules that need to be activated before they can join. This often involves adding a functional group (like a hydroxyl or carboxyl group) that will participate in the bonding process.
2. Dehydration Synthesis (or Condensation Reaction):
- Two activated monomers join together, releasing a molecule of water (H₂O) in the process. This water molecule is formed by removing a hydroxyl group (-OH) from one monomer and a hydrogen atom (-H) from the other. This creates a covalent bond between the monomers, forming a dimer.
3. Polymerization:
- The process of adding monomers continues, forming a chain that grows longer and longer. This chain is the polymer.
4. Types of Polymers:
- Linear polymers: Monomers link in a straight chain.
- Branched polymers: Side chains branch off the main chain.
- Cross-linked polymers: Chains are linked together by covalent bonds, forming a network structure.
Breaking down a polymer requires the opposite process – hydrolysis. This means adding water back into the molecule to break the bonds.
Here's how it works:
1. Water Molecule Added:
- A water molecule interacts with the covalent bond between two monomers.
2. Bond Broken:
- The water molecule breaks the bond, with one hydrogen atom attaching to one monomer and the hydroxyl group attaching to the other.
3. Monomers Separated:
- The polymer is broken down into individual monomers.
Examples:
* Carbohydrates: Glucose monomers are joined by dehydration synthesis to form starch or glycogen. When we digest these polymers, hydrolysis breaks them back down into glucose.
* Proteins: Amino acid monomers are joined by dehydration synthesis to form protein chains. Hydrolysis breaks down proteins into amino acids during digestion.
* Nucleic Acids: Nucleotides are joined by dehydration synthesis to form DNA or RNA. Hydrolysis breaks down these polymers during DNA replication or transcription.
In summary, building polymers involves joining monomers through dehydration synthesis while breaking them down requires hydrolysis. This delicate balance allows for the creation and breakdown of complex biological molecules essential for life.
