(5) But hemoglobin does not exhibit hyperbolic binding, as we assumed in Problem

Question

(5) But hemoglobin does not exhibit hyperbolic binding, as we assumed in Problem 4; its oxygen-binding curve has a sigmoidal shape. The quantity n is known as the Hill coefficient, and its value increases with the degree of cooperation of the ligand (in this case, oxygen) binding. For hemoglobin, the value of n is approximately equal to 3. We can use the equation for hemoglobin’s sigmoidal oxygen binding to calculate the fractional saturation of hemoglobin. At a CO2 partial pressure of 5 torr, the p50 value for hemoglobin is 15 torr.
(a) What is the fractional saturation when pO2 = 25 torr, a typical venous oxygen partial pressure?
(b) What is the fractional saturation when pO2 = 120 torr, a typical oxygen partial pressure in the lungs?

Explanation / Answer

We know that,

Fractional saturation YO2 = pO2/(p50+pO2)

I) pO2 = 25 torr, p50= 15torr

YO2 = 25/(15+25) = 5/8

II) pO2= 120 torr, p50= 15 torr

YO2 = 120/(15+120) = 8/9

Related Questions

Navigate

• Browse (All)
• Browse #
• Subjects

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