Final answer:
Among the options given, steroid hormones are the exception as they are not lipophobic; they are lipophilic and can diffuse through cell membranes to interact with internal receptors. The other options—Nitric oxide, Epinephrine, and Prostaglandins—are hydrophilic and cannot diffuse through the plasma membrane.
Step-by-step explanation:
The student question is asking which of the given options does not describe a lipophobic, which is also the same as hydrophilic, chemical messenger. Lipophobic chemical messengers are those that cannot dissolve in lipids and thus cannot diffuse through the plasma membrane, which makes them hydrophilic as they are able to dissolve in water. Lipophilic messengers, in contrast, can diffuse through cell membranes due to their ability to dissolve in lipids.
The exception among the options provided is steroid hormones, like estradiol or testosterone, which are derived from cholesterol and are indeed lipophilic or lipid-soluble. Since they can diffuse across cell membranes, they interact with receptors located inside the target cells, as opposed to the surface receptors that lipophobic messengers would bind to.
For example, epinephrine is an amino acid-derived hormone, and it is hydrophilic, not able to diffuse through cell membranes. Nitric oxide (NO) and prostaglandins are also hydrophilic and would therefore require surface receptors on target cells. However, steroid hormones, being lipophilic, are able to pass through the plasma membrane and interact with intracellular receptors, making them the exception in the list provided.