Corso - taste, olfaction, and vision

Most cells depolarize due to influx of postively charged sodium ions. How are these olfactory cells are different. How do they depolarize?

a. outflow of positively charged potassium ions

b. outlow of negatively charged chloride ions

c. outflow of positively charged sodium ions

b.

In classical systems using G-alpha-s, the cAMP activates PKA, how is this different for these olfactory cells? In olfactory cells:

a. cAMP activates PKB

b. cAMP activates PKC

c. cAMP opens inward calcium ion channels

d. cAMP opens inward chloride ion channels

e. cAMP activates PKG

c.

For the sweet taste cells, how do they differ from the classical G-alpha-s system?

a. cAMP activates PKB

b. PKA phosphorylates an inward chloride channel, blocking the inward chloride leak. this depolarizes the cell

c. PKA phosphorylates an outward potassium channel, blocking the outward potassium leak. this depolarizes the cell

c.

what does cGMP do in the phototransduction cascade?

permits positively charged sodium and calcium ions into the retinal cells

what does activated rhodopsin do in the phototransduction cascade?

activates a G-protein (transducin)

what does activated transducin do in the phototransduction cascade?

activates a phosphodiesterase

what does the phosphodiesterase in retinal cells do in the phototransduction cascade?

converts cGMP to GMP

what does light do in the phototransduction cascade?

converts cis-retinal into all-trans-retinal

how do odorants lead to cell depolarization?

odorant binds receptor

activates G-protein

activates adenylyl cyclase (AC)

makes cAMP

opens calcium channels

calcium opens outward chloride channels

cell depolarizes

how do taste molecules lead to cell depolarization?

taste molecule binds to receptor

activates G protein

activates adenylyl cyclase (AC)

makes cAMP

activates PKA

phosphorylates outward potassium channels

inside of cell becomes positive (depolarized)

how does light lead to cell depolarization?

light causes retinal w/in rhodopsin to convert to all-trans retinal

this activates the rhodopsin protein

rhodopsin activates G protein (transducin)

activated transducin activates phosphodiesterase (PDE)

PDE breaks down cGMP

cell polarizes without cGMP and stops releasing glutamate

what happens to cells in the dark (vision)?

cGMP keeps sodium/calcium channels open

cell depolarizes —> releases glutamate

what happens to cells in the light (vision)?

cGMP converted to GMP

calcium channels close

cell polarized —> stops releasing glutamate