2. Buffers. Physiological pH inside of living cells is about 7.4. The total free

Question

2. Buffers. Physiological pH inside of living cells is about 7.4. The total free concentration of phosphate inside of cells is about I mM. Phosphate exists in four different protonation states (se the figure below, taken from your textbook). H,PO HPO,2 PoA pK,-2.12 PK,-7.21 pK, 12.67 A) Which form of phosphate is the most abundant at physiological pH? B) Suppose that 100 ml of cellular extract is treated with 50 ml of 0.5 mM HCI. What is the final plH? LAssume that the HCl reacts only with the phosphate buffer in the cell extract.] Which form of phosphate is most abundant now?

Explanation / Answer

A. At physiological pH-7.4 the phosphate form is HPO2-4.

B. pH = pKa + log10([A-]/[HA])

        HCL concentration is X = 0.5mM X 50ml / 100 ml

                                           = 0.25mM

       Phospahte concentration is 1mM

    pH = 7.21 + log10([0.25]/[1])

          = 7.21 - 0.60

          = 6.6

At pH 6.6 the phosphate present is H2PO4-

Related Questions

Navigate

• Browse (All)
• Browse 2
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.