Harper's Illustrated Biochemistry, Volume 1 - Murray R. 1993

Biomolecules and Biochemical Methods
Major Classes of Natural Molecules

As can be seen from Table 2.2, the major complex Biomolecules present in the Cells and Tissues of higher animals (including humans) are DNA, RNA, Proteins, Polysaccharides, and Lipids. These complex molecules are built from simpler biomolecules, which are also listed in the table. The Building Blocks of DNA and RNA (collectively known as Nucleic Acids) are deoxynucleotides and ribonucleotides, respectively. The building blocks of proteins are Amino Acids. Polysaccharides are constructed from simple CARBOHYDRATES; specifically, Glycogen (the principal polysaccharide found in human tissues) is built from glucose. Fatty acids can be considered the building blocks of lipids, although lipids are not strictly polymers of fatty acids. DNA, RNA, proteins, and polysaccharides are referred to as Biopolymers because they consist of repeating building blocks (monomers). These complex molecules constitute a substantial part of the "stuff of life"; much of this book will be devoted to describing the various properties of biomolecules—both biopolymers and monomers. Similar types of complex molecules are found in lower organisms, although their building blocks, in some cases, may differ somewhat, as shown in Table 2.2. For example, Bacteria lack glycogen and triacylglycerols, but contain other polysaccharides and lipids.

Class="center">Table 2.2. Major complex organic biomolecules present in cells and tissues. Nucleic acids, proteins, and polysaccharides are polymers constructed from the building blocks also indicated in the table. Lipids, generally speaking, are not biopolymers, and Fatty acids are not used as their building blocks in all cases.