Compare and contrast the mechanisms of actions of lipid soluble vs water soluble hormones.

Expert Answers
ncchemist eNotes educator| Certified Educator

Hormones are small molecules that travel throughout the body and act as chemical messengers.  They are responsible for regulating body activities like growth, sexual functions, and digestion.  Hormones can vary widely in their chemical structures.  Water soluble hormones are generally amino acid and peptide based in structure and are relatively soluble in water.  They travel freely in the bloodstream but cannot pass through nonpolar cellular membranes.  As a result, they tend to bind to receptors on the surface of the membrane which then sends a chemical signal into the cell to elicit a response.

Lipid (or fat) soluble hormones are generally steroid based in structure.  They do not dissolve in blood plasma so they usually travel through the bloodstream while bound to water soluble proteins.  But when they reach the target cell, they can diffuse through the membrane to act on an internal receptor in the cell.  That is the main difference in the mechanism of action.

nerdygirl-1996 | Student

lipid soluble hormones are steroid hormones. These hormones act on cells  by diffusing through the lipid portion of the cell membrane  and combining with receptor proteins inside the cell.  These recptors may be on the mitchondria, nucleus or other cell organelles. The steroid hormone-receptor complex may then change the functioning of  cells by changing the type, activities and quantities of proteins produced.

Protein and amine hormones are not soluble in the lipid bilayer of the cell membrane and so work by attaching to receptore proteins on the membrane of the target cell. The combination of the hormone with the receptor protein stimulates the secretion of a secondary messenger substance  which diffuses through the cell to activate particular enzymes.

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