Question

A hormone circulating in the blood with target tissue 1, 2 and 3 could act selectively on target tissue 1 if:
A. Target tissue 1 had fewer hormone receptors than 2 and 3.
B. Target tissue 2 and 3 had hormone receptors with a higher hormone affinity than target tissue 1.
C. Target tissue 1 had hormone receptors with a greater hormone affinity than target tissue 2 and 3.
D. The hormone was released only in the vicinity of target tissue 1.

Answer 1

Hint: Hormone receptors are present on the target site and hormones bind with it to produce their effect. They are of two types:- membrane-bound receptors and intracellular receptors. Membrane-bound receptors are those receptors which are present on the cell membrane of the target tissue whereas intracellular receptors which are present inside the target cells. Receptors are specific in nature as only 1 hormone is specific to the receptors. In reaching the target tissue, hormones bind with the receptor forming hormone-receptor complex.

Complete Step by Step Answer:
As hormones are poured directly into the bloodstream, they are distributed throughout the blood. All the target tissue in the blood experiences the same hormone concentration. Any hormone will bind with the target tissue only if it contains more number of receptors or receptors with greater hormone affinity. Thus, hormones circulating in the blood with target tissue 1, 2 and 3 could act preferably only on target tissue 1 if target tissue 1 had receptors with a higher hormone affinity.

The correct option is C.

Note: Certain biochemical changes occur in the target tissue after the formation of hormone-receptor complex. These hormones regulate the metabolism and physiological changes in the target tissue. Hormones are divided into different groups on the basis of their chemical nature as peptide, steroidal, iodothyronines and amino-acid derivatives. The membrane-bound receptors associated hormones do not enter the target cell but they release secondary messengers which regulate cellular metabolism. The hormone associated with the intracellular receptors controls gene expression or chromosome function. Biochemical actions generated lead to physiological and developmental effects.