Final answer:
The test for an absolute threshold for taste is detecting one teaspoon of sugar in two gallons of water, which measures the minimum intensity at which a substance can be detected. Sour taste receptors are sensitive to the pH of saliva, and taste receptors are specific to each of the five primary tastes. Gustation and olfaction share the characteristic of having specific receptors for environmental stimuli and similar transduction mechanisms.
Step-by-step explanation:
The test that measures the absolute threshold for taste is detecting one teaspoon of sugar dissolved in two gallons of water. An absolute threshold refers to the minimum intensity at which a stimulus can be detected 50% of the time. In the realm of gustation, or the sense of taste, detecting very low concentrations of a substance, like sugar, in a large volume of water, is one way to measure this threshold.
For sour taste, the submodality that is sensitive to the pH of saliva is sour, as acidic environments increase hydrogen ion (H+) concentrations that affect the taste receptors. Taste receptors are found in taste buds on the tongue and are specific to the primary tastes: salty, sour, sweet, bitter, and umami. When we discuss gustation, we focus on how these receptors bind with specific molecules, like the binding of sweet tastants to their G-protein coupled receptors in the case of the sweet taste.
Olfaction, or the sense of smell, is similar to gustation because both involve receptors that are specific to certain stimuli in the environment, and both utilize a form of transduction to communicate the presence of these stimuli to the brain.