Taste

Question 1

What do the 6 categories of taste receptors detect?

Answer 1

• sweetness (molecules of sugar)
• umami (molecules of glutamate/glutamine)
• bitterness (a variety of molecules)
• saltiness (positive ions such as sodium)
• sourness (pH level; the concentration of free hydrogen ions)
• fat (fatty acids)

Question 2

What is sweetness detected with?

Answer 2

• detected with a single metabotropic receptor

Question 3

What is umami detected with?

Answer 3

• detected with a single metabotropic receptor

Question 4

What is bitterness detected with?

Answer 4

• detected with 50 different metabotropic receptors that bind different bitter molecules

Question 5

What is saltiness detected with?

Answer 5

• detected with an ion channel that is highly permeable to sodium

Question 6

What is sourness detected with?

Answer 6

• detected with an ion channel that is highly permeable to free protons
• cells that detect sourness are also responsible for the detection of astringency (e.g., the flavor of “salty licorice”) and carbonation (bubbles), but the details are murky

Question 7

What is fat detected with?

Answer 7

• detected with metabotropic receptors and fatty acid transporters

Question 8

How do we perceive gustatory information?

Answer 8

• when a tasted molecule binds to a taste receptor protein, it produces a change in membrane potential
• different tastes relate to the activation of different types of taste receptor proteins

Question 9

What are taste buds?

Answer 9

• contain 20 to 150 taste receptor cells

Question 10

What are taste receptor proteins?

Answer 10

• do not have traditional action potentials
• release neurotransmitter in a graded fashion
• replaced about every ten days, because they are directly exposed to a rather hostile environment

Question 11

What does research with mice and the sugar receptor gene demonstrate?

Answer 11

• much of taste processing is innate

Question 12

Which taste receptor cells are instinctively rewarding/reinforcing?

Answer 12

• sugar
• umami

Question 13

Which taste receptor cells are instinctively aversive?

Answer 13

• bitter
• can grow to appreciate some bitter taste cell activity, but it is an acquired taste

Question 14

Where is the primary gustatory cortex?

Answer 14

• in the insula lobe of the cerebral cortex