Suppose the circulating concentration of hormone is 10-10 M and the Kd for bindi

Question

Suppose the circulating concentration of hormone is 10-10 M and the Kd for binding to its receptor is 10-8 M. What faction of the receptors will have hormone bound? If a meaning full physiological response occurs when 50% of the receptors have bound a hormone molecule, how much will the concentration of hormone have to rise to elicit a response? We assume that the Law of Mass Action holds and that the chemical reaction is given thus:

R + H <--> RH The dissociation constant, Kd, is equal to ([R][H])/[RH]

Explanation / Answer

Answer:

R + H <--> RH The dissociation constant, Kd, is equal to ([R][H])/[RH]

At a circulating concentration of hormone equal to 10^–10 M, about 1% of the receptors will have a bound hormone molecule {[R–H]/[R]total = 10^–10 M/(10^–10 M + 10^–8 M) = 0.0099}.

50% of the receptors will have a bound hormone molecule when the concentration of hormone equals the Kd; that is, at 10^–8 M {[R–H]/[R]total = 10^–8 M/(10^–8 M + 10^–8 M) = 0.5}.

Thus, the hormone concentration will have to rise 100-fold to elicit a response.

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

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