Question

Sour taste is perceived by which receptors?

• A. T1R1
• B. T1R2
• C. T1R3
• D. TRPP3

Hint:

Sour taste is detected by TRPP3 receptors, which are activated by acidic substances like citric acid found in lemons and other sour foods.

Answer 1

The Correct Option is D

Step 1: Separate the two receptor families in taste.
Taste modalities use two broad mechanisms. Sweet and umami rely on the T1R G-protein-coupled receptor family (T1R1/T1R2/T1R3 combinations), whereas sour and salty are detected through ION CHANNELS that sense protons and sodium directly. Recognising that sour is an ion-channel modality immediately steers us away from the T1R options.

Step 2: Recall what sour actually is.
Sourness is the taste of acidity - acids release hydrogen ions (H$^+$) in solution. Detecting sour therefore means sensing intracellular acidification/protons in the taste receptor cell, a job for a proton-sensitive channel, not for a sweet/umami GPCR.

Step 3: Name the channel and discard the T1R options.
The sour-sensing taste cells use the TRPP3 (PKD2L1) channel to transduce the acid signal into a neural response. By contrast: T1R1 (with T1R3) mediates umami, T1R2 (with T1R3) mediates sweet, and T1R3 is the shared partner subunit of those sweet/umami complexes - none of them encodes sour.

Final answer: Sour taste is perceived by the TRPP3 (Option 4) channel.