ABSTRACT
The purpose of this final chapter is to present a brief summary of the main classes of biopolymers, i.e., polysaccharides, proteins, and polynucleotides, including their chemical structures, their conformational preferences, and their biological functions. In each instance, we compare and contrast their structures, conformations, and behaviors to those of the structurally much simpler synthetic polymers we have dealt with in the preceding chapters. Emphasis is placed on the importance of the drastically greater variety and specificities of biopolymer structures, which lead to a similarly expanded range of behaviors in comparison to those of the structurally much simpler and more primitive synthetic polymers. Crucial among these comparisons is the ability of single or two or more biopolymer chains of proteins and polynucleotides to undergo phase transitions in response to their environments. This unique ability confers upon certain biopolymers the ability to organize into and/or form living structures and/or to control various life functions, such as their repetitive and reproducible syntheses, control of molecular chemical and/or physical processes, etc. Proteins (synthetic polymers) are generally assigned four levels of structure: primary structure or amino acid sequence (microstructure), secondary structure (local conformations), tertiary structures (overall sizes and shapes), and quaternary structure (morphologies of semi-crystalline homopolymers and phase-segregated block-copolymers). In short, with almost limitless structural diversity and specificity, biopolymers provide dramatic examples of Inside polymer chain microstructure ←→ Outside polymer material property or function relationships employed by Nature to create complex living organisms.
