BackThe Structure and Function of Large Biological Molecules (Chapter 5 Study Notes)
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Molecules of Life
Introduction to Biological Macromolecules
Living organisms are composed of four major classes of large biological molecules: carbohydrates, lipids, proteins, and nucleic acids. These molecules are essential for structure, function, and regulation of the body's tissues and organs.
Carbohydrates: Serve as fuel and building material.
Lipids: Diverse group, mainly hydrophobic, important for energy storage and membrane structure.
Proteins: Perform a wide range of functions including catalysis, defense, transport, and support.
Nucleic acids: Store and transmit hereditary information.
Polymers are large molecules made by linking together smaller units called monomers. Carbohydrates, proteins, and nucleic acids are polymers, while lipids are not true polymers.
Macromolecules: Polymers and Monomers
Polymer Formation and Breakdown
Most biological macromolecules are polymers, which are long chains of repeating units (monomers). The process of building and breaking down polymers is central to cellular function.
Polymer: A long molecule consisting of many similar or identical building blocks linked by covalent bonds.
Monomer: The repeating unit that serves as a building block for a polymer.
Dehydration Reaction (Synthesis of Polymers)
Monomers are joined together by dehydration reactions, which remove a water molecule to form a new bond.
Example equation:
Hydrolysis (Breakdown of Polymers)
Polymers are broken down into monomers by hydrolysis, which adds a water molecule to break a bond.
Example equation:
Carbohydrates
Structure and Function
Carbohydrates are organic molecules that include sugars and their polymers. They serve as energy sources and structural materials in cells.
Monosaccharides: The simplest carbohydrates, also known as simple sugars (e.g., glucose, fructose).
Disaccharides: Formed by joining two monosaccharides via a glycosidic linkage (e.g., sucrose, maltose).
Polysaccharides: Large polymers composed of many monosaccharide units (e.g., starch, cellulose, glycogen).
Monosaccharides generally have molecular formulas that are multiples of (e.g., glucose is ).
Functions:
Major fuel for cellular work.
Serve as raw material for building other molecules.
Structural support in plants (cellulose) and animals (chitin).
Types of Carbohydrates
Type | Structure | Example | Function |
|---|---|---|---|
Monosaccharide | Single sugar unit | Glucose | Energy source |
Disaccharide | Two sugar units | Sucrose | Transported in plants |
Polysaccharide | Many sugar units | Starch, Cellulose | Energy storage, structure |
Additional info: Carbohydrates can be classified based on the number of sugar units: monosaccharides (one), disaccharides (two), and polysaccharides (many).
