CHAPTER 7 - Macromolecules: Small Changes and Large Effects

Abstract

This chapter focuses on two types of polymers: (1) DNAs and (2) proteins. The structure of DNA and proteins of molecule are usually discussed in terms of their primary, secondary, and tertiary structures. Primary structure details which atoms are bonded to which atoms and is usually expressed as a list of connected nucleotides (DNA) or amino acids (protein). Entropy would ensure that proteins and nucleic acids did not remain as linear molecules in their natural aqueous environment. In fact energetic factors are also at work with the result that the molecules usually exist as well-defined structures. Secondary structure describes well-defined geometrical units of connected nucleotides or amino acids. Tertiary structure deals with the geometry of the molecule as a whole. Thus, for DNA, the primary structure is concerned with what phosphates, sugars, and bases are present; the formation of bases into base-pairs and the angles between the bases is the province of secondary structure, while the tertiary structure relates to how the DNA helices are packed together.