Researchers studying olfactory and taste receptors have stumbled upon an unusual phenomenon. These receptor proteins are sometimes expressed in other animal tissues in addition to the nose or tongue. For example, the sweet taste receptor T1R2 is expressed in the pancreas. Suggest the best possible explanation for these findings.
A. Damaged receptors are recycled by the body and end up in waste-disposal organs.
B. Control of protein expression is imperfect. As long as a receptor doesn't interfere with organ function, expression will not be selected against.
C. Chemoreceptors bind molecules that help the body sense and respond to internal phenomena, such as sugar levels in the blood.
D. Techniques used to visualize protein expression are imperfect and may lead to false positive results.
Clarify Question
What is the key concept addressed by the question?
What type of thinking is required?
Gather Content
What do you already know about taste receptors? What other information is related to the question?
Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
C. Chemoreceptors bind molecules that help the body sense and respond to internal phenomena, such as sugar levels in the blood.
Clarify Question
What is the key concept addressed by the question?
· Why are sensory receptors sometimes internal?
What type of thinking is required?
o This is an evaluate question because you have to weigh and judge the different reasons that taste receptors could be found internally in the body.
Gather Content
What do you already know about taste receptors? What other information is related to the question?
· You already know that that taste receptors are specific to different types of chemical that elicit different flavors (sweet, salty, umami, bitter). You know that sweet receptors like T1R2 are activated by sugars such as sucrose and fructose and artificial sweeteners like saccharin. We know that the pancreas cannot taste in the same sense that our tongue can, so why would it have taste receptors? The pancreas is an organ in the digestive system that produces important hormones such insulin and glucagon which are vital for controlling blood sugar. Since sugars bind to T1R2 receptors, these receptors could be involved in monitoring and regulating blood sugar, which is vitally important as individuals with diabetes can attest.
Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
· The pancreas is both an endocrine organ, producing hormones, and a digestive organ, producing enzymes that help to digest food. Thus referring to it as a waste-disposal organ is not very accurate. It is true that protein expression is not always perfect, but cells will avoid wasting energy producing receptors that they do not need. Thus it is unlikely that cells will produce unneeded receptors without any negative consequences. Techniques used to visualize protein expression may lead to background fluorescence or staining, but that is why controls are necessary to avoid false positives. The most logical answer is that chemoreceptors like T1R2 in the pancreas bind to molecules to help monitor blood sugar levels.
Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
o Answering this question correctly depended upon your ability to weigh or judge the potential reasons that T1R2 receptors are expressed in the pancreas. If you answered incorrectly, which answer did you choose? Did you think that damaged receptors would be recycled by the pancreas? Did you forget that T1R2 receptors are taste receptors that detect sugars?
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