CHAPTER 2

THE STRUCTURE AND FUNCTION OF MACROMOLECULES

Polymer principles

1. Most macromolecules are polymers

2. An immense variety of polymers can be built from a small set of monomers

• Cells join smaller organic molecules together to form larger molecules.

• These larger molecules, macromolecules, may be composed of thousands of atoms and weigh over 100,000 daltons.

• The four major classes of macromolecules are: carbohydrates, lipids, proteins, and nucleic acids.

Introduction

• Three of the four classes of macromolecules form chainlike molecules called polymers.

• Polymers consist of many similar or identical building blocks linked by covalent bonds.

• The repeated units are small molecules called monomers.

• Some monomers have other functions of their own.

1. Most macromolecules are polymers

• The chemical mechanisms that cells use to make and break polymers are similar for all classes of macromolecules.

• Monomers are connected by covalent bonds via a condensation reaction or dehydration reaction.

• One monomer provides a hydroxyl group and the other provides a hydrogen and together these form water.

• This process requires energy and is aided by enzymes.

• The covalent bonds connecting monomers in a polymer are disassembled by hydrolysis.

• In hydrolysis as the covalent bond is broken a hydrogen atom and hydroxyl group from a split water molecule attaches where the covalent bond used to be.

• Hydrolysis reactions dominate the digestive process, guided by specific enzymes.

• Each cell has thousands of different macromolecules.

• These molecules vary among cells of the same individual, even more among unrelated individuals of a species, and are even greater between species.

• This diversity comes from various combinations of the 40-50 common monomers and other rarer ones.

• These monomers can be connected in various combinations like the 26 letters in the alphabet can be used to create a great diversity of words.

• Biological molecules are even more diverse.

2. An immense variety of polymers can be built from a small set of monomers