Final answer:
Peptide hormones cannot penetrate the cell membrane but instead bind to external receptors, triggering a signaling cascade inside the target cell. This involves various messengers that amplify the hormone's signal, leading to specific cellular responses, such as changes in enzyme activity or gene expression.
Step-by-step explanation:
How Do Peptide Hormones Generate a Response in the Target Cell
Peptide hormones elicit a response in target cells via a specific signaling pathway, as they are not lipid-soluble and cannot pass directly through the cell membrane. When such a hormone, such as insulin, is released in response to a stimulus (e.g., high blood glucose levels), it travels through the bloodstream to its target cells. Upon reaching a target cell, the peptide hormone binds to specific receptors located on the cell's plasma membrane.
This binding triggers a cascade of events inside the cell involving various molecules that act as 'messengers.' The hormone itself is known as the first messenger, which, upon binding to the receptor, leads to the activation of a G-protein on the inside of the cell's membrane. This G-protein then activates or generates a secondary messenger such as cyclic AMP (cAMP). The secondary messenger carries the signal into the interior of the cell, where it can prompt various cellular activities. These activities can include the stimulation of protein synthesis, altering the permeability of the cell membrane, or influencing cell growth and division, among other possible responses.
Through these layered steps of signaling, the initial message from the peptide hormone is amplified and results in a precise and regulated cellular response, ensuring that the body's systems function in harmony.