(8/25/10) - Review of pH

1. Recognize the 20 amino acids that commonly occur in proteins and classify them according to ionization potential.

2. Define the terms: cationic, anionic and zwitterionic.


 * Cationic: when the AA has a positive charge (generally on the amino group) it can donate an H ion- so its technically an acid.


 * Anionic: when the AA is negatively charged (on the carboxyl group) it can receive an H ion. Can be considered the conjugate base of the cationic ‘acid’.


 * Zwitterionic: when the AA has both a positive and negative charge on it ( - on carboxyl, + on amino) It has locations that can give and receive H ion

3. Explain the meaning of the terms pKa and pI as they apply to amino acids and proteins.
 * pKa: is the –log of the equilibrium constant. The pKa is the pH at which 50% of the molecules are in the protonated form and 50% are in the unprotonated form. At this point the molecule is the best buffer solution b/c it can best donate and receive protons.


 * pI: isoelectric point- pH at which the zwitterion exists and the positive and negative species on each molecule are in equal concentration. So the overall protein carries no net charge.

4. Recognize that cellular enzymes require specific pH conditions to function and therefore the body must create compartmentalization.

5. Appreciate the pH differences throughout the body and its ability to modulate pH when exposed to the widely varying pH of dietary, fluid, drug, and other resources.

6. Briefly describe in a single sentence the role of the lungs, red blood cells and kidneys in maintaining acid-base balance.

7. Explain the nature of the bicarbonate buffer, hemoglobin buffers and intracellular buffers.

8. Describe the respiratory and metabolic components of the acid-base balance.

9. Define acidosis and alkalosis.
 * Acidosis- excessive buildup of acid in the blood or body- could be because the lungs aren’t blowing off the CO2 enough.


 * Alkalosis- high alkalinity of the blood (low pH)- could be due to insufficient kidney function or hyperventilation.