Know the difference between lipid soluble and water soluble hormones and how they elicit their effects on target cells.

Water soluble hormone binds to the membrane bound receptors whereas lipid soluble hormones bind to the internal/intracellular receptors.

Explanation:

Hormones are called regulators because they can either stimulate or inhibit the target cell's activity.

They perform their action by binding to specific protein on target tissue called hormone receptors. Each receptor is specific for a particular hormone. The hormone-receptor complex bring about the biochemical changes in the target cell.

Hydrophillic or water soluble hormones interact with the membrane bound receptors. They result in the generation of secondary messengers such as cyclic AMP. Secondary messengers bring about the cascading action amplifying the final effect. That is why even a very small quantity of hormone is sufficient for a powerful cascading effect.

Lipid soluble hormones can diffuse through the plasma membrane and thus they bind to the intracellular receptors. The hormone-internal receptor complex enters the mucleus and regulates gene expression. Example: steroid hormones and thyroid hormones.