B1.1.3 Digestion of polymers into monomers by hydrolysis reactions Notes

What Is Hydrolysis?

1. A water molecule splits into –H and –OH.
2. These fragments attach to the exposed ends where the bond was broken, preventing the monomers from reconnecting.

The Role of Hydrolysis in Digestion

Hydrolysis is vital for breaking down large macromolecules (polymers) into smaller monomers that the body can absorb.

1. Polysaccharides → Monosaccharides
   1. Starch or glycogen (long chains of glucose) are hydrolyzed by enzymes (e.g., amylase, maltase).
   2. Glycosidic bonds are broken, releasing glucose units.
2. Polypeptides → Amino Acids
   1. Proteins (chains of amino acids linked by peptide bonds) are digested by pepsin, trypsin, etc.
   2. Each bond is cleaved by adding water, yielding free amino acids.
3. Nucleic Acids → Nucleotides
   1. DNA and RNA (linked by phosphodiester bonds) are broken down by nucleases.
   2. The result is nucleotide monomers (building blocks of genetic material).

Why Is Water Essential?

1. Splitting H₂O: The –H and –OH derived from water block the ends of newly formed monomers, stabilizing them.
2. Preventing Rebonding: These newly attached groups stop the monomers from re-polymerizing.
3. Universal Solvent: Water’s presence in cells makes hydrolysis feasible in aqueous environments.

Hydrolysis vs. Condensation

1. Condensation (Dehydration Synthesis)
   1. Removes water to form bonds, building polymers from monomers.
2. Hydrolysis
   1. Adds water to break bonds, splitting polymers back into monomers.
3. Together, hydrolysis and condensation form a biological cycle:
   1. Condensation assembles large molecules for storage or function.
   2. Hydrolysis disassembles them to release nutrients or energy.

Applications of Hydrolysis in the Body

1. Energy Release: ATP hydrolysis liberates energy for cellular processes.
2. Detoxification: The liver uses hydrolysis to break down toxic substances.
3. Biomolecule Recycling: Cells reuse monomers by hydrolyzing older or damaged molecules.