Gustation

Question 1

What are the 5 human tast classes?

Answer 1

• Salty - proper electrolyte balance
• Sweet - energy rich nutrients
• Umami - amino acids
• Bitter+Sour - potentially noxious or poisonous
• Fatty? - satiety, combination of somatosensory and gustation

Question 2

What are the three types of papillae on your tongue?

Answer 2

• circumvallate
• foliate
• fungiform

Question 3

Describe taste buds

Answer 3

• Onion shaped structure containing 50-100 tast receptor cells
• Pore opens out to the surface of the body
• Apical surface - folded into microvillli (increase SA)

Question 4

What is the inability to tast called?

Answer 4

Ageusia

Question 5

Describe signal transduction for salty tastes.

Answer 5

• Na⁺ in mouth increases
• Membrane potential depolarizes
• Ca²⁺ channels opened/NT release

Question 6

Describe signal transduction for a sour taste.

Answer 6

• Apically localized K⁺ channels blocked by protons
• Receptor comprised of two parts
  
  • TRPP3 and PDK1L3
• Results in depolarization and opening of Ca²⁺ channels

Question 8

Which 3 tast classes activate the phospholipase C pathway and are G protein coupled?

Answer 8

Sweet, umami and bitter

Question 9

Which GPRC do sweet tastants bind to?

Answer 9

T1R2, T1R3

Question 10

Which GPRC do umami tastants bind to?

Answer 10

T1R1, T1R3

Question 11

Which GPRC do bitter tastants bind to?

Answer 11

T2R

Question 13

Which pathway is activated by L-glutamate and other amino acids as well as MSG?

Answer 13

Umami

Question 14

Describe the mechanism/pathway that sweet, bitter and umami tastants induce.

Answer 14

Question 15

What are the three major classes of taste cells?

Answer 15

• Type I glial cell
• Type II receptor cell (ATP release, sweet/umami/bitter)
• Type III presynaptic cell

Question 16

Why does airplane food taste awful?

Answer 16

• Dryness and low pressre decrease our abilities to taste (sweet, salty)
• Loud noises also decrease ability
• Low humidity means that we are able to smell poorly

Question 17

In arthropods (invertebrates), taste receptors are located where?

Answer 17

Sensilla (antenna) - found all over body; probiscus, mouth, wing, margin, vaginal plases…

Question 18

Insects use _____ to transduce taste.

Answer 18

GPRC

Question 19

Like their olfactory neirons, in Drosophila, each gustatory receptor neuron expresses _______.

Answer 19

Only one receptor (unlike humans and worms)

Question 20

What are the four groups of gustatory cells in H. reamuri, a terrestiral crutacean?

Answer 20

• sugar cells
  
  • several sugars and e-glucosides
• calcium cells
  
  • excited by CaC12
• amino acid cells
  
  • responding to asparganine and methionine
• ? cells
  
  • aq rinse of desert woodlice and noth to other stimuli tested

Question 21

In worms, gustation is mediated by…

Answer 21

Amphid sensory organs