Final answer:
Water-soluble hormones are hydrophilic molecules that bind to surface receptors of target cells, triggering signaling pathways inside the cell that result in cellular changes. They usually produce rapid but short-term effects and like ADH, can regulate processes such as water reabsorption in the kidneys.
Step-by-step explanation:
Water-soluble hormones are types of hormones that cannot pass through the lipid bilayer of the cell membrane due to their hydrophilic nature. To exert their effects, these hormones bind to receptors on the surface of target cells, initiating a cascade of intracellular events that lead to the desired cellular response. This mechanism of action involves a series of steps starting with the hormone (often referred to as the first messenger) binding to its receptor on the cell membrane. The activated receptor then interacts with G proteins, leading to the production of a second messenger such as cyclic AMP (cAMP) inside the cell.
cAMP activates a series of proteins called protein kinases, which in turn phosphorylate other proteins within the cell, modifying their activity. This can result in various responses such as production of enzymes, alteration of cell function, or changes in gene expression. Because of this indirect action, water-soluble hormones are typically associated with rapid but short-term effects on cells.
An example of a water-soluble hormone regulating body processes is the peptide hormone antidiuretic hormone (ADH). ADH is produced by the hypothalamus and, when released, it instructs the kidneys to reabsorb water, thereby reducing urine output and helping to maintain blood volume and pressure. This is an instance of a hormone affecting an osmoregulatory process.