The dissociation constant Kd for ligand binding to the receptor

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The dissociation constant Kd for ligand binding to the receptor is 10^–7 M. The concentration of ligand required for occupying 10% of receptors is

1. 10^–6 M
2. 10^–7 M
3. 10^–8 M
4. 10^–9 M

Correct Option: C

Given,
Dissociation constant, K_d = 10^–7M
The reaction is: L + R → LR
Thus, Kd for the reaction = [L][R]/[LR]
or [LR]/[LR][R] = 10/100
Therefore, [L] = 1/9 * 10^–7M = 10^–8M