Final answer:
The pathway in a gustatory epithelial cell in response to a bitter tastant involves the activation of G-protein coupled receptors (GPCRs). Bitter tastants bind to these receptors, leading to either depolarization or hyperpolarization of the gustatory cells. Therefore correct option is C
Step-by-step explanation:
In response to a bitter tastant, the correct part of the pathway that occurs in a gustatory epithelial cell is C) Activation of G-protein coupled receptors (GPCRs). Bitter taste, similar to sweet, involves the binding of molecules to G-protein coupled receptors located on taste cells. Through a signal transduction system, these receptors activate gustatory cells, which may result in their depolarization or hyperpolarization depending on the specific bitter molecule.
Bitter and sweet tastants are not detected by the activation of sodium channels or by binding to sweet taste receptors, nor is serotonin specifically mentioned as a neurotransmitter released by gustatory cells in response to bitter stimuli. Instead, after activation by the bitter tastant, gustatory cells release neurotransmitters onto the dendrites of sensory neurons, which carry the taste information to the brain.