Final answer:
Lipids, specifically small hydrophobic ligands, are important in chemical messaging. They can directly diffuse through the plasma membrane and interact with internal receptors. Examples include steroid hormones like estradiol, testosterone, and cholesterol.
Step-by-step explanation:
Lipids are an important group of lipid-based molecules that are important in chemical messaging. Specifically, small hydrophobic ligands are lipid-soluble ligands that can directly diffuse through the plasma membrane and interact with internal receptors. Examples of small hydrophobic ligands include steroid hormones such as estradiol, testosterone, and cholesterol. These lipids serve as chemical messengers and play a crucial role in signaling pathways.