Final answer:
For a water-soluble hormone, the last event after signaling through the target cell's membrane receptors involves the creation of proteins that modify the cell's function. These proteins are the result of a signal transduction pathway activated by the hormone's initial binding to the cell surface receptor, and the hormones do not enter the nucleus or interact directly with DNA.
Step-by-step explanation:
When a water-soluble hormone approaches its target cell, several events will occur in sequence to transmit the hormone's message. Firstly, the hormone, acting as a first messenger, will bind to a receptor on the cell membrane since it cannot pass through the lipid bilayer. This initiates a cascade of intracellular signaling events involving second messengers, such as cyclic AMP (cAMP). These second messengers activate a series of proteins and enzymes, which are integral for signal transduction through the cytoplasm. As part of this cascade, certain proteins in the cell will be phosphorylated to change the cell's activity.
The last event in this sequence is the creation of proteins by the target cell. These proteins, potentially including enzymes or other functional proteins, lead to the alteration of the cell's function in response to the hormone signal. These proteins are produced after the entire signaling cascade has been completed, beginning from the hormone binding to the receptor and finishing with the cellular activities being modified. Unlike lipid-soluble hormones, water-soluble hormones do not interact directly with the cell's DNA in the nucleus, so the last significant event is the creation of responsive proteins within the cytoplasm, rather than direct interaction with DNA.