Question

Why is the hydrolysis of lipids by lipase important?
How can i create a buffer solution with ph 9.5 and 3.5?

Answer 1

Alimentary triacylglycerols must be degraded to fatty acids and monoacylglycerols before absorption by the intestinal mucosa. This breakdown is carried out by the small intestine lipases.

To make a usable buffer one should use acid or base with pK close to necessary pH values.

pH for buffers formed by weak base and its salt:

$$\mathrm{pH} = 14 - \mathrm{pK_b} + \lg [\mathrm{B}] / [\mathrm{HB_+}]$$

To obtain pH 9.5 the ammonia buffer should be used (pKb = 4.75):

$$9.5 = 14 - 4.75 + \lg [\mathrm{NH_3}] / [\mathrm{NH_{4+}}]$$ $$[\mathrm{B}] / [\mathrm{BH_+}] = 10_{0.25} = 1.78$$

Therefore, we should take 1.78 moles of ammonia for each mole of ammonia salt, such as ammonia chloride.

pH for buffers formed by weak acid and its salt:

$$\mathrm{pH} = \mathrm{pK_a} + \lg [\mathrm{A}] / [\mathrm{HA}]$$

To obtain pH 3.5 the racemic tartaric acid buffer should be used (pKa1 = 3.22):

$$3.5 = 3.22 + \lg [\mathrm{C_4H_5O_6}] / [\mathrm{HC_4H_5O_6}]$$ $$[\mathrm{C_4H_5O_6}] / [\mathrm{HC_4H_5O_6}] = 10_{0.28} = 1.91$$

Therefore, we should take 1.91 moles of sodium or potassium tartrate for each mole of tartaric acid.