BackThe 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 molecules: carbohydrates, lipids, proteins, and nucleic acids, focusing on their structures, functions, and the relationships between their monomeric and polymeric forms.
Concept 5.1: Macromolecules are Polymers, Built from Monomers
Definition and Overview
Macromolecules are large molecules composed of thousands of covalently connected atoms. The three main classes of macromolecules are carbohydrates, proteins, and nucleic acids.
A polymer is a long molecule consisting of many similar or identical building blocks linked by covalent bonds.
The repeating units that serve as building blocks are called monomers.
Lipids are the fourth class of large biological molecules but are not considered true polymers.
Examples of Biological Molecules
Carbohydrates: Monomer = Glucose; Polymer = Starch
Proteins: Monomer = Amino acid; Polymer = Protein (e.g., alcohol dehydrogenase)
Nucleic acids: Monomer = Nucleotide; Polymer = DNA or RNA
Lipids: Not true polymers; example = Phospholipid
Key Points
Macromolecules are critical for cellular structure and function.
Carbohydrates, proteins, and nucleic acids are polymers made from monomers.
Lipids are large molecules but do not form polymers in the same way.
Example: Alcohol Dehydrogenase
Alcohol dehydrogenase is a protein (enzyme) that catalyzes the breakdown of alcohols in the body.
Its structure is composed of amino acid monomers linked into a specific three-dimensional shape, enabling its function.
Additional info:
Polymers are synthesized by dehydration reactions and broken down by hydrolysis (covered in later sections).
The diversity of macromolecules arises from the arrangement of a small set of monomers into complex structures.
