0.5 Bis2a 02.appendix ii detailed look at acid-base equilibrium  (Page 9/8)

A more detailed look at acid-base chemistry

An important note about this module

Acids and bases are very common substances whose properties vary greatly. Many acids are known to be quitecorrosive, with the ability to dissolve solid metals or burn flesh. Many other acids, however, are not only benign but vital to theprocesses of life. Far from destroying biological molecules, they carry out reactions critical for organisms. Similarly, many basesare caustic cleansers while many others are medications to calm indigestion pains.

In this concept study, we will develop an understanding of the characteristics of molecules which make themeither acids or bases. We will examine measurements about the relative strengths of acids and bases, and we will use these todevelop a quantitative understanding of the relative strengths of acids and bases. From this, we can develop a qualitativeunderstanding of the properties of molecules which determine whether a molecule is a strong acid or a weak acid, a strong baseor a weak base. This understanding is valuable in predicting the outcomes of reactions, based on the relative quantitative strengthsof acids and bases. These reactions are commonly referred to as neutralization reactions. A surprisingly large number of reactions,particularly in organic chemistry, can be understood as transfer of hydrogen ions from acid molecules to base molecules.

The point of this module is for you to become familiar with the concepts of acids and bases and how as biologist we use them in understanding how molecules interact with each other and the environment. You do not need to memorize any equations or tables, but you should be able to use the tables and understand conceptually what is is meant when we say, a specific carboxyl group has a pKa of 2.2. Think of this as an extension to our discussion on water and pH; primarily because water can be thought of as an acid and a base. Remember that water can ionize into a hydroxyl ion (OH-) and a Hydronium ion (H3O+), which is the basis for pH.

What is the role in bis2a of acid-base chemistry