Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because .

This question lacks options, the options are:

A) only target cells retain the appropriate DNA segments

B) intracellular receptors are present only in target cells

C) only target cells possess the cytosolic enzymes that transduce the testosterone

D) only in target cells is testosterone able to initiate the phosphorylation cascade leading to activated transcription factor

The correct answer is B.

Explanation:

Receptors are proteins that can be found in the nucleus, cytoplasm, or cytoplasmic membranes. Receptors bind to a ligand with high specificity and high affinity. In some fat-soluble signal molecules, they bind to specific protein receptors located on the surface of the target cells they affect. These surface protein receptors bind the signal molecule (or ligand) with a high affinity, and transform this extracellular event into one or more intracellular signals, which alter the behavior of the target cell. Testosterone needs to be transported in the blood through proteins, which is why only 3% is in free form, while the remaining 97% is bound to proteins, among which the sex hormone transporter globulin and the albumin, it enters cells very easily and binds to androgen receptors (intracellular receptors generally found in the cytoplasm), significantly stimulating protein synthesis, among many other processes.