Final answer:
Taste receptor cells in terrestrial vertebrates are clustered into groups called taste buds, which house chemoreceptor cells sensitive to various tastes. These tastes include sweet, salty, sour, bitter, and umami, each detected by specific types of receptors.
Step-by-step explanation:
In terrestrial vertebrates, taste receptor cells are clustered into groups known as taste buds. Taste buds are small structures on the tongue that contain chemoreceptor cells, which are sensitive to chemicals in food. Within these taste buds, the gustatory receptor cells make contact with food chemicals through openings called taste pores. When tasting, these receptor cells activate sensory neurons that are part of the facial and glossopharyngeal nerves, allowing us to perceive different tastes such as sweet, salty, sour, bitter, and umami.
Each primary taste has a specific type of receptor, with transduction mechanisms reflecting the molecular composition of the tastant. For example, salty tastants provide sodium ions that directly excite taste neurons, sour tastants are acidic and increase hydrogen ion concentration in taste neurons, and sweet, bitter, and umami tastants require a G-protein coupled receptor.