Here's why:
* Hormones act as chemical messengers: They are produced by endocrine glands and travel through the bloodstream to reach their target cells.
* Target cells have specific receptors: These receptors are proteins on the surface of the cell or inside the cell that bind to the hormone.
* Binding triggers a response: Once the hormone binds to the receptor, it triggers a specific response within the target cell, like:
* Changes in gene expression
* Activation of enzymes
* Alteration of cell membrane permeability
* Stimulation of cell division or differentiation
Example: Insulin is a hormone that regulates blood sugar levels. Its target cells are primarily liver, muscle, and fat cells. These cells have insulin receptors that allow them to respond to insulin's signal and take up glucose from the bloodstream.
