Question

15.) The gallbladder is an intriguing if often overlooked organ that stores bile for the liver in a variety of vertebrates. A biochemically interesting aspect of the gallbladder is that it is one of the few places in the body that regularly has a basic pH. To study enzymatic processes that occur there, appropriate pH conditions must be replicated. The complicating aspect is that the pH is not uniform throughout the entirety of the gallbladder system, where it can range from pH 7.6 to pH 8.5. Conveniently, the buffer range of the H(Tris)+/Tris conjugate pair overlaps well with this system, having a pKa of 8.02. This pKa is convenient to many biological systems, hence its use as a buffer for many experiments.a)What is the full buffer range of the H(Tris)+/Tris system?b)Describe the preparation of two Tris buffer solutions, one for the high end and one for the low end of the gallbladder pH. Make both buffers to a total buffer concentration of 0.110 M with a volume of 1 liter.

Answer 1

Tris(hydroxymethyl) aminomethane is known as tris. Tris is highly water soluble and his aqueous solution is basic in nature due to the presence of -NH2 group. The pH range for tris buffer is 7-9 given in the literature is derived by experiments and the equation used for is pH = pKa +  log[(A-/HA)].

To prepare gallbladders high end and low end pH (i.e. pH 7.6 and 8.5 ) solutions, we required the following materials:

1] Tris(hydroxymethyl) aminomethane

2] Distilled water

3} dil. HCl solution

The desired concentration and volume of solution is 0.110 M and 1L.

Therefore we have to calculate, the weight of tris required for to preparation of a 1L solution of 0.110M tris.

The molecular weight of tris = 121.14gm

for 1M sol. 121.14 gm of tris in 1L of water.

therefore, for 0.110M sol. (121.14 x 0.11) = 13.325gm tris in 1L of water.

For, Tris buffer Solution (pH 7.6)

Take approximately, 1/3 or 1/2 water of the final volume of solution and add 13.325gm of tris to it. Dissolve the tris in water and add dil. HCl solution dropwisely, till pH becomes 7.6 and make the final volume of solution to 1L.

For, Tris buffer Solution (pH 8.5)

Take approximately, 1/3 or 1/2 water of the final volume of solution and add 13.325gm of tris to it. Dissolve the tris in water and add dil. HCl solution dropwisely, till pH becomes 8.5 and make the final volume of solution to 1L.