Which of the following are not the tastes of the tongue?
1. Sweet
2. Bitter
3. Salty
4. Spicy
5. Umami
6. Sour
7. Pungent
Select the correct answer using the codes given below.

Question

UnlockIAS · Accepted Answer

Correct — C, 4 and 7. Sensory physiology recognises exactly five basic tastes — sweet, sour, salty, bitter and umami — and the word 'basic' has a precise meaning: each has its own dedicated receptor on the taste-receptor cells inside a taste bud, and its own labelled pathway to the brain. Sweet is detected by the T1R2–T1R3 receptor pair and umami by T1R1–T1R3, both G-protein-coupled receptors; bitter by the T2R family, of which humans carry about twenty-five working genes; sour by the proton channel OTOP1, which senses hydrogen ions; and salty largely by the epithelial sodium channel ENaC responding to Na+ ions. That accounts for five of the seven items in the list — 1 Sweet, 2 Bitter, 3 Salty, 5 Umami and 6 Sour. What is left is 4 Spicy and 7 Pungent, and they are not tastes at all; they are the same single sensation named twice, which is precisely the examiner's design. The burn of a chilli comes from capsaicin binding TRPV1, a receptor whose ordinary job is to report temperatures above roughly 43 °C and physical pain; black pepper's piperine and mustard oil's allyl isothiocyanate act on the same receptor family. Crucially, these receptors sit on the free nerve endings of the trigeminal nerve, not on taste buds. That is why the sensation is classed as chemesthesis rather than gustation, why you can feel it on your lips, your eyes and broken skin where there is not a single taste bud, and why cold milk, whose fat dissolves capsaicin, relieves it while water merely spreads it. The split is therefore clean and anatomical: five entries are tastes carried from taste buds by cranial nerves VII, IX and X, and two entries — spicy and pungent — are irritation carried by cranial nerve V along ordinary pain fibres.

Why the other options are wrong — (a) Gets item 7 right and then discards two genuine tastes. Bitter (2) is the most protective of the five — the T2R family exists largely to make plant alkaloids and spoiled food unpalatable. Umami (5) is the real trap: it was named by Kikunae Ikeda at Tokyo Imperial University in 1908 from kombu seaweed broth, but only became textbook-standard after its receptor was identified around 2000, so candidates drilled on the old four-taste list still treat it as a marketing word rather than a basic taste.  (b) Correctly spots Spicy (4) and then throws out Sweet (1) and Salty (3), the two least disputable tastes on any classification anywhere. A candidate lands here by finding one non-taste, assuming the answer must have three items because two of the four options do, and filling the rest at random — or by inverting the stem and answering 'which of these ARE tastes'.  (d) Names Salty (3) and Sour (6), both of which are basic tastes with well-characterised transduction machinery — sour through OTOP1 proton channels in type III taste cells, salty through amiloride-sensitive ENaC sodium channels. This option contains no non-taste at all, so it fails on both items rather than one, and it is chosen mainly by candidates who confuse a taste with the chemical that produces it.

Concept: Taste, or gustation, is a chemical sense mediated by taste buds — clusters of 50 to 100 receptor cells buried in the fungiform papillae at the front of the tongue, the foliate papillae along its sides and the large circumvallate papillae arranged in a V at the back. The filiform papillae that give the tongue its rough texture carry no taste buds at all. Only five stimulus classes have dedicated receptors there, and those five are the basic tastes. Everything else we loosely call taste is either smell — retronasal olfaction, which supplies most of what we experience as 'flavour', and whose loss during a cold is why food goes bland — or chemesthesis, the chemical irritation of ordinary pain, touch and temperature fibres of the trigeminal nerve. Capsaicin, piperine, menthol and mustard oil all work this last way, on TRP-family ion channels that also respond to heat and cold. The distinction is not pedantry: it explains why chilli hurts the eye, why menthol feels cold without lowering temperature, and why a person who has lost their sense of smell can still detect salt and sugar perfectly well.

State PCS 2023 Q7 — Science & Technology PYQ with Answer

State PCS 2023 Q7 — Science & Technology PYQ with Answer