AP BIOLOGY

Detailed explanation-1: -It is thought that, because of their lipophilic nature, free steroid hormones enter target cells primarily by passive diffusion through the cell membrane. After gaining entry to the cell, steroid hormones act as ligands for nuclear receptors and alter gene transcription (reviewed in [4]).

Detailed explanation-2: -Steroid hormones can pass through the plasma membrane by simple diffusion because they are lipid derived hormones, which means that they are capable of passing through every cell of our body. Unlike other types of hormones, steroid hormones do not have to bind to plasma membrane receptors.

Detailed explanation-3: -The steroid hormones, being fat soluble (hydrophobic), must be bound to and carried around by transport proteins (like albumin and globulins which are blood proteins produced by the liver). Free (unbound) hormones are able to enter target organs.

Detailed explanation-4: -Steroids are overall hydrophobic because of their common tetracyclic hydrocarbon core (Figure 1G).

Detailed explanation-5: -Explanation: Steroid hormones are nonpolar and hydrophobic, whereas peptide hormones are polar and hydrophilic. This means that the steroid hormones cannot dissolve in water but peptide hormones can dissolve in water.