Final answer:
Changes in cell secretion are likely to occur more rapidly in response to an extracellular signal when compared to increased cell division. This is because cell secretion can directly activate signaling pathways that lead to quick cellular responses, whereas cell division requires a series of events to occur, which takes longer.
Step-by-step explanation:
The selection of the phrase in each pair that is likely to occur more rapidly in response to an extracellular signal depends on the cellular processes involved. When comparing changes in cell secretion and increased cell division in response to an extracellular signal, the former is likely to occur more rapidly.
Changes in cell secretion can occur quickly because they often involve the direct activation of signaling pathways that trigger the movement of vesicles and the release of substances from the cell. An example of this would be the binding of epinephrine (adrenaline) to a G-protein-linked receptor, which can rapidly upregulate cellular metabolism.
In contrast, increased cell division requires activation of a series of events like growth factor binding to receptor tyrosine kinases (RTKs), activation of the MAP kinase pathway, and eventual expression of proteins that interact with other cellular components to initiate cell division. This process is generally slower than immediate changes in cell secretion, as it includes progression through the cell cycle, DNA replication, and other complex steps.