Introduction
Many biological processes are pH dependent, to illustrate, stomach is at a relatively lower pH than other organs for proper function of digestive enzymes. In particular, buffer is essential for maintaining cellular functions. For instance, protein intake and metabolism generates about 70mM of H+ daily (Silverthorn, Johnson, Ober, Garrison, & Silverthorn, 2012), which could lower pH of human blood to as low as 3. To limit the drastic change in blood pH, human body has three buffer systems – bicarbonate, monohydrogen phosphate, and ammonia. Buffer is made up of weak acid and its conjugate base. The pH of a buffer is determined by the ratio of unprotonated and protonated species, as described by the Henderson-Hasselbalch Equation:
Since buffer in its buffering region contains both unprotonated and protonated species that can accept and donate protons, respectively, it resists sudden change in concentration of protons accompanying with the addition of certain amount of strong acid or base depending on the buffer capacity. Generally, the best buffer region is at pH = pKa ± 1 (BCH370 Lab Manual, 2015 Fall). Above all, the goal of this lab is to understand how pH is changed relative to pKa in real life …show more content…
Different charged species are formed when the change in pH of AA solution lead to protonation or deprotonation of the ionizable groups. The first part of this lab was to identify the unknown AA #3 which contains an ionizable side chain by constructing its titration curve using standard acid solution and standard alkali solution. Titration curve of the AA around its buffering regions would expect to have regions of small slope. A blank water titration curve was also determined by measuring the amount of acid or base consumed in titrating water and for finding out the true titration curve of the unknown
Many biological processes are pH dependent, to illustrate, stomach is at a relatively lower pH than other organs for proper function of digestive enzymes. In particular, buffer is essential for maintaining cellular functions. For instance, protein intake and metabolism generates about 70mM of H+ daily (Silverthorn, Johnson, Ober, Garrison, & Silverthorn, 2012), which could lower pH of human blood to as low as 3. To limit the drastic change in blood pH, human body has three buffer systems – bicarbonate, monohydrogen phosphate, and ammonia. Buffer is made up of weak acid and its conjugate base. The pH of a buffer is determined by the ratio of unprotonated and protonated species, as described by the Henderson-Hasselbalch Equation:
Since buffer in its buffering region contains both unprotonated and protonated species that can accept and donate protons, respectively, it resists sudden change in concentration of protons accompanying with the addition of certain amount of strong acid or base depending on the buffer capacity. Generally, the best buffer region is at pH = pKa ± 1 (BCH370 Lab Manual, 2015 Fall). Above all, the goal of this lab is to understand how pH is changed relative to pKa in real life …show more content…
Different charged species are formed when the change in pH of AA solution lead to protonation or deprotonation of the ionizable groups. The first part of this lab was to identify the unknown AA #3 which contains an ionizable side chain by constructing its titration curve using standard acid solution and standard alkali solution. Titration curve of the AA around its buffering regions would expect to have regions of small slope. A blank water titration curve was also determined by measuring the amount of acid or base consumed in titrating water and for finding out the true titration curve of the unknown