Final answer:
The last event to happen when a water-soluble hormone approaches its target cell is that the target cell makes proteins that alter the cell's function, following a series of signal transduction events initiated by hormone binding to the cell's surface receptor.
Step-by-step explanation:
When a water-soluble hormone approaches its target cell, it goes through several steps to elicit a response. Initially, the hormone binds to a receptor on the surface of the target cell, as it cannot penetrate the lipid bilayer due to its hydrophilic nature. This binding initiates a signal transduction pathway within the cell, involving second messengers like cyclic AMP (cAMP) and protein kinases. Ultimately, this causes the phosphorylation of proteins within the cytoplasm, leading to a variety of cellular responses, such as the production of proteins that alter the cell's function.
Given that hydrophilic hormones can't enter the cell, they do not directly interact with the cell's DNA within the nucleus. Therefore, among the options provided:
- The hormone's signal will be transduced through the cytoplasm of the target cell (a)
- The hormone's signal will interact with the target cell's DNA (b)
- The target cell will make proteins that alter the cell's function (c)
- The hormone's signal will enter the nucleus (d)
The last event to occur in the sequence for a water-soluble hormone would be an option (c), the target cell will make proteins that alter the cell's function, as this is the final result of the signal transduction pathway initiated by the hormone binding to the membrane receptor.