뒤로The Structure and Function of Large Biological Molecules
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Chapter 5: The Structure and Function of Large Biological Molecules
Introduction
Large biological molecules, also known as macromolecules, are essential to the structure and function of all living organisms. This chapter explores the four major classes of biological macromolecules: carbohydrates, proteins, nucleic acids, and lipids. Understanding their structure and function is fundamental to the study of biology.
Macromolecules: Polymers and Monomers
Definition and Overview
Macromolecules are large molecules composed of thousands of covalently connected atoms.
Most macromolecules are polymers, which are long chains made up of repeating subunits called monomers.
Three of the four major classes—carbohydrates, proteins, and nucleic acids—are true polymers. Lipids are not considered true polymers or macromolecules, but are still large and biologically important.
Example: Starch (a carbohydrate) is a polymer of glucose monomers.
Synthesis and Breakdown of Polymers
Dehydration Reaction: A chemical reaction in which two monomers are covalently bonded to each other with the removal of a water molecule. This process builds polymers from monomers.
Hydrolysis: The reverse of dehydration. Polymers are broken down into monomers by the addition of water, breaking the covalent bond.
Equation for Dehydration Synthesis:
Equation for Hydrolysis:
The Four Major Classes of Biological Molecules
Overview Table
Class | Monomer (if applicable) | Polymer (if applicable) | Example |
|---|---|---|---|
Carbohydrates | Monosaccharide | Polysaccharide | Starch, Cellulose |
Proteins | Amino acid | Polypeptide | Enzymes, Hemoglobin |
Nucleic Acids | Nucleotide | Polynucleotide | DNA, RNA |
Lipids | — | — | Fats, Phospholipids, Steroids |
Additional info: Lipids are not true polymers because they are not made from repeating monomer units in the same way as the other three classes.
Key Concepts Illustrated
Figure 5.1a: Biological Molecules
Carbohydrates, proteins, and nucleic acids are polymers made from monomers.
Lipids are large molecules but are not polymers.
Figure 5.2: Synthesis and Breakdown of Polymers
Shows the process of dehydration synthesis (building polymers) and hydrolysis (breaking polymers).
Dehydration removes a water molecule to form a new bond; hydrolysis adds a water molecule to break a bond.
Summary
Macromolecules are essential to life and are built from smaller units called monomers.
Dehydration reactions build polymers; hydrolysis breaks them down.
Carbohydrates, proteins, and nucleic acids are true polymers; lipids are not.
