CHEMISTRY 420/520 – Principles of Biochemistry Instructor: Professor Anthony S. Ionic equilibria; pH; buffers Interactions between macro-ions in solution. • Buffers • Biological Buffer. 40 FUNDAMENTALS OF BIOCHEMISTRY Note that the pH scale is logarithmic, not arithmetic. Thus, when the pH of a solution decreases. Biochemistry Laboratory Manual Chemistry Department Peru State College. This handout is designed to test you ability to properly prepare solutions (buffers).

Water, pH, and Non-Covalent Bonding pH Ionization of Water Proton hopping in water Sometimes the hydrogen of one water molecule will 'jump' to another water molecule: H 2O + H 2O H 3O + + OH - This proton hopping is called the ionization of water (an ion is a positively or negatively charged atom or molecule). This ionization creates a H 3O + and a OH - molecule. The H 3O + is often written as simply H +. This is because a H 3O + is just a H + that jumps from one water molecule to another: H 2O H + + OH - So remember, H 3O + = H + Looking at either of the two chemical equations above, it is important to note that the reverse reaction is also occurring. How much H + and OH - exist in water? Very, very little!

The ratio of either H + or OH - to H 2O in neutral water is 1:1,000,000,000! Since this is such a small amount of either H + or OH -, they rarely meet and neutralize each other. The equilibrium constant, K eq describes the ionization equilibrium of water: K eq = [H +][OH -] Because of this relationship it is important to note that if the [H +] goes up then the [OH -] must go down, and vice-versa, for the value for the K eq of water must remain constant. For neutral water, the K eq is 1 x 10 -14 M and the concentrations of [H +] and [OH -] are each 1 x 10 -7 M.

Let's look at that last number without the exponent: 0.0000001 M This is obviously a very small number. A more manageable way to discuss small numbers such as this is to take the negative logarithm. For the concentration of [H +], this is called the pH. In this case: -log(0.0000001 M) = 7 The pH of a solution is simply the negative logarithm of [H +]. The pH of a solution describes the acidity of a solution. Acidic solutions are those with a pH of less than 7 and basic solutions have a pH greater than 7.

A solution, like H 2O, with a pH = 7 is neutral. Similarly, the pOH could be used to describe a solution in terms of its OH - concentration. POH is the negative logarithm of the OH - concentration. One useful thing to remember is. PH + pOH = 14.

In the body, the pH of blood is 7.4. This corresponds to a [H +] of about 40 nM. This value can only vary from 37 nM to 43 nM without serious metabolic consequences. PKa In living systems, much of the chemistry involves interactions between acids and bases. Acids are H + donors and bases are H + acceptors. HA H + + A - Acid and base reactions are made up of conjugate acid-base pairs.

Strong acids are those that readily give up a H +. Strong bases readily accept a H +. Weak acids do not readily give up a H +, but will under the right conditions. A weak base is one that does not easily take up a H +. The conjugate base for a strong acid is a weak base. In contrast, a strong base has a weak acid as its conjugate. Think of a strong acid as a person with an ugly wig.

This person can't wait to get rid of this! Equilibrium Unemployment As A Worker Discipline Device Pdf Printer. So now we have a wig (H +) and a person without the wig (the weak base). You can understand that the person without the wig doesn't really want to take it back! However, what about strong base-weak acid conjugate pairs?