Final answer:
Hydrophobic chemical messengers can pass through the plasma membrane due to their compatibility with the hydrophobic interior of the lipid bilayer, enabling them to diffuse into cells where they often affect gene expression.
Step-by-step explanation:
Yes, hydrophobic chemical messengers can easily travel through cell membranes if they are small enough because their water-hating nature is akin to the interior of the lipid bilayer of the membrane. The plasma membrane is composed of a lipid bilayer, which has hydrophilic (water-loving) heads facing outward and hydrophobic (water-hating) tails facing inward. This amphiphilic structure creates a barrier that prevents hydrophilic substances from passing through without assistance. However, hydrophobic substances align well with the interior of the membrane and can diffuse through more freely.
Examples of such messengers are steroid hormones like testosterone and estradiol, as well as other molecules like vitamin D and thyroid hormones. These hydrophobic molecules can pass through membranes and often bind to intracellular receptors that may act as transcription factors, impacting gene expression. For their travel through the bloodstream, these hydrophobic ligands typically bind to carrier proteins, as their solubility in water is low.