Overview
This lecture explains how biological macromolecules are synthesized and broken down, focusing on dehydration synthesis and hydrolysis reactions, and their regulation by enzymes.
Biological Macromolecules: Overview
- Biological macromolecules are large, carbon-based molecules essential for life.
- The four major classes are carbohydrates, lipids, proteins, and nucleic acids.
- They are organic, usually containing carbon, hydrogen, oxygen, and sometimes nitrogen or other minor elements.
- Macromolecules make up most of a cell's dry mass.
Dehydration Synthesis (Condensation)
- Monomers are single subunits that bond together to form polymers.
- Dehydration synthesis joins monomers by forming covalent bonds and releasing water.
- In this reaction, a hydrogen atom from one monomer and a hydroxyl group from another combine to make water.
- The process requires energy and produces larger polymers from smaller monomers.
- A single monomer type like glucose can create various polymers (e.g., starch, glycogen, cellulose).
Hydrolysis
- Hydrolysis breaks down polymers into monomers by adding water.
- The reaction splits covalent bonds; one fragment gains a hydrogen atom and the other gains a hydroxyl group.
- Hydrolysis is essentially the reverse of dehydration synthesis.
- This process releases energy and is common during digestion.
Role of Enzymes
- Dehydration and hydrolysis reactions are catalyzed by specific enzymes.
- Each macromolecule class is broken down by its corresponding enzyme type.
- Examples: amylase breaks down carbohydrates; proteases (like pepsin) break down proteins; lipases break down lipids.
- Enzyme-catalyzed hydrolysis in digestion makes nutrients available for absorption and energy use.
Key Terms & Definitions
- Macromolecule — a large molecule formed by the joining of smaller molecules, usually by a condensation (dehydration synthesis) reaction.
- Monomer — a small molecule that can join with other similar molecules to form a polymer.
- Polymer — a large molecule formed from many monomers joined together.
- Dehydration Synthesis — a chemical reaction that builds larger molecules from smaller units by removing water.
- Hydrolysis — a chemical reaction that breaks polymers into monomers by adding water.
- Enzyme — a protein that speeds up (catalyzes) chemical reactions in living organisms.
Action Items / Next Steps
- Review visual representations of dehydration synthesis and hydrolysis online.
- Prepare for further study of each macromolecule type in upcoming sections.