Q-1. Largest gene family so for described in mammals
a) Immunoglobin
b) T cell receptor
c) Odorant receptor
d) Taste receptor
Answer: Odorant receptor
Explanation:
The genes that code for about 1000 different types of odorant receptors make up largest gene family so for described in mammals- larger than immunoglobin and T cell receptor gene families combined.
Q-2. Odorant receptors are coupled to
a) Heterotrimeric G protein
b) Ionotropic glutamate receptor
c) Amiloride sensitive epithelial sodium channel (ENaC)
d) Metabotropic glutamate receptor
Answer: Heterotrimeric G protein
Explanation:
Odorant receptors are coupled to heterotrimeric G proteins.
When an odorant molecule binds to its receptor, the G protein subunits (Alpha, beta and gamma) dissociate.
The alpha subunits activates adenylate cyclase to catalyze the production cyclic AMP which acts as a second messenger to open cation channels, causing an in-word directed Ca++ current.
Q-3. Salt and sour tastes is perceived by
a) Glutamate receptor
b) Metabotropic receptor
c) Ionotropic receptor
d) G protein coupled receptor
Answer: Ionotropic receptor
Explanation:
Taste and taste receptor:
Salt taste: Amiloride sensitive epithelial sodium channel (ENaC)
Sour taste: Amiloride sensitive epithelial sodium channel (ENaC)
Umami taste: Metabotropic glutamate receptor (mGluR4) and Ionotropic glutamate receptor
Sweet taste: G protein coupled receptor
Q-4. Umami taste is perceived by
a) Glutamate receptor
b) Metabotropic receptor
c) Ionotropic receptor
d) G protein coupled receptor
Answer: Metabotropic receptor
Explanation:
See above explanation.
Important point:
All tastants are sensed from all parts of tongue and adjacent structures.
Q-5. All of the following are concerned with taste pathways except:
a) Anterior Insula-Frontal Operculum
b) Ventral postero-medial nucleus of thalamus
c) Nucleus of the soli
d) Lateral lemniscus
Answer: Lateral lemniscus
Explanation:
Taste Pathways:
Chorda tympani branch of facial nerve (Anterior two third of tongue), Glosso-pharyngeal nerve (Posterior one third of tongue) and Vagus nerve from other than tongue-> Nucleus of the solitary tract-> Ipsilateral medial lemniscus -> Ventral postero-medial nucleus of thalamus -> Gustatory cortex (Anterior Insula-Frontal Operculum)
Q-6. Ageusia and pypogeusia is caused by
a) Vitamin B3 deficiency
b) Zinc deficiency
c) Cisplatin
d) All
Answer: All
Explanation:
Ageusia and pypogeusia is caused by:
Cisplatin and captopril
Vitamin B3 and Zinc deficiency
Damage to lingual or Glosso-pharyngeal nerve
Q-7. Which of the following has minimum threshold concentration for taste sensation?
a) Strychnine
b) Saccharin
c) HCL
d) Glucose
Answer: Strychnine
Explanation:
Substance and taste threshold:
Strychnine (Bitter taste):1.6
Saccharin (Sweet): 23
HCL (Sour): 100
NaCl (Salt): 2000
Sucrose (Sweet): 10,000
Glucose (Sweet): 80,000