Which of the following is true about gustatory receptors?
A In order for a chemical to be sensed it must be hydrophobic.
B The receptors generate an action potential in response to painful stimuli.
C In order for a chemical to be sensed it must be hydrophilic.
D Complete adaptation in a human occurs in about 60 minutes.
E All gustatory receptors have the same threshold for activation.
The correct answer and explanation is :
The correct answer is E: All gustatory receptors have the same threshold for activation.
Explanation:
The gustatory system, which is responsible for our sense of taste, is highly specialized and involves specific receptors that detect different types of tastes. These receptors are located on the taste buds, which are found on the tongue, the roof of the mouth, and in the throat. Each taste bud contains multiple taste receptor cells, each of which responds to one of five basic tastes: sweet, salty, sour, bitter, and umami.
However, not all gustatory receptors have the same threshold for activation. A threshold refers to the minimum concentration of a substance required to activate the receptor and produce a detectable taste sensation. Different taste receptors have different thresholds for activation depending on the type of taste they detect.
For example:
- Sweet and umami receptors generally have a lower threshold, meaning that only small concentrations of sugar or glutamate (found in umami foods like meat and cheese) are needed to stimulate these receptors.
- Bitter receptors, on the other hand, have a higher threshold and are more sensitive to low concentrations of bitter compounds, which is believed to be an evolutionary mechanism to protect us from consuming potentially toxic substances, as many poisonous compounds have a bitter taste.
- Sour and salty receptors also have varying thresholds, but these are generally intermediate between the extremes of sweet and bitter.
The concept of different thresholds for different tastes helps explain why some flavors, like sweetness, are easier to detect in small amounts, while others, like bitterness, require higher concentrations to be perceived. Therefore, the statement that all gustatory receptors have the same threshold for activation is incorrect, as it overlooks the variability in receptor sensitivity depending on the type of taste.