Phototransduction Cascade

Question 1

When there are no light photons hitting rod cells, it is turned ___.

Answer 1

On

Question 2

In this dark state, _____ binds to the cationic channels to allow influx of Na+, Ca+, etc

Answer 2

cGMP

Question 3

Inward “dark current” keeps photoreceptors relatively ____?

Answer 3

Depolarized

Question 4

The outer segment plasma membrane consist of what 2 channels?

Answer 4

cGMP-gated cationic channels and Na/Ca/K exchanger

Question 5

What is the resting potention of the photoreceptor?

Answer 5

30-40mV

Question 6

What are the 3 main components of the phototransduction pathway?

Answer 6

Rhodopsin, Transducin and Phosphodiesterase

Question 7

What is the role of rhodopsin?

Answer 7

The visual pigment

Question 8

What is the role of Transducin?

Answer 8

A g-protein which elicits the 2nd signal of the cascade

Question 9

What is the role of phosphodiesterase?

Answer 9

Catalyzes cGMP to GMP

Question 10

What is the activated form of rhodopsin?

Answer 10

Metarhodopsin II

Question 11

When a photon of light his 11-cis-retinal, what happens next?

Answer 11

The light energy causes a conformational change to all-trans-retinal

Question 12

When the cationic channels close, this causes the cell to ____.

Answer 12

Hyperpolarize and turns off

Question 13

T or F: Cones adapt to light more effectively than cones.

Answer 13

True

Question 14

1 PDE hydrolyzes ____ GMP molecules.

Answer 14

2000

Question 15

1 Rhodopsin activates ___ transducin molecules

Answer 15

500

Question 16

When a rod cells is on, a bipolar cell is ___. (and vice versa)

Answer 16

off

Question 17

Cone response to a single photon is __ ______.

Answer 17

Not detectable

Question 18

Single photon response in cones is ____-fold smaller than in rods.

Answer 18

100-fold

Question 19

True or False: Cone response shows faster response kinetics than Rods.

Answer 19

True