BIOLOGY Volume 1 - A Guide to General Biology - 2004

3. CHEMICAL COMPONENTS OF LIVING MATTER

3.1. Introduction to Biochemistry

3.1.3. Macromolecules

Simple organic molecules often serve as building blocks for the synthesis of larger macromolecules. A macromolecule is a giant molecule formed by many repeating units. Molecules constructed in this way are called polymers, and the constituent units are known as monomers. The joining of individual units together—a process known as Condensation—involves the removal of Water. The reverse process, The breakdown of polymers, occurs via Hydrolysis, i.e., through The addition of water. Living organisms contain three Major Types of macromolecules: Polysaccharides, Proteins, and Nucleic Acids. Their respective monomers are Monosaccharides, Amino Acids, and NUCLEOTIDES.

Macromolecules account for approximately 90% of a Cell's dry weight. Polysaccharides serve as energy reserves and perform structural Functions, whereas proteins and nucleic acids act as "informational molecules." This means that the sequence of monomer units is crucial in proteins and nucleic acids, and it varies much more than in polysaccharides, whose composition is usually limited to one or two Different types of subunits. The reasons for this will become clear later. In this chapter, we will examine all three classes of macromolecules and their subunits in detail. We will also include Lipids in this Structure/133.html">Discussion—molecules that are generally much smaller, yet likewise built from simple organic molecules (see Fig. 3.4).