nov.12 pt4 Flashcards Preview

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Flashcards in nov.12 pt4 Deck (18):
1

what happens when light hits outer segment of photoreceptor?

change in RMP

2

RMP of photoreceptor cell

minus forty mV

3

light causes __ in membrane of photoreceptor cells

HYPERPOLARIZATION

4

example of change in RMP in photoreceptor cells

minus 40mV to minus 65mV

5

cGMP gated channels of photoreceptor cells are ____ when its dark

open

6

advantage of metabtropic receptors in photoreceptors

amplification

7

three steps of PHOTOTRANSDUCTION

1. activation of visual pigment ie photoreceptor by light 2. activated photopigment triggers biochemical signalling pathway leading ot reduction of cGMP 3. closure of cGMP gated channels and hyperpolarization

8

cGMP gated channels are

nonselective cation channels

9

reversal potential of the cGMP gated channels

0

10

photopigment consists of

opsin and vitamin A aldehyde AKA 11-cis retinal

11

opsin is this type of protein

GPCR

12

opsin is covalently linked to

lysine

13

opsin is light sensitive when

attached to 11-cis retinal

14

light has this effect on rhodopsin

conformational change to 11-trans retinal, triggering conformation change in opsin

15

what happens to retinal after photoisomerization

dissociate from opsin, transported out of photoreceptor cells, taken up into epithelial cells, converted back to 11-cis retinal, and transported back

16

when GTP binds alpha subunit of G protein

alpha dissocaites from beta gamma, g alpha then activates PDE, hydrolyzing cGMP to GMP

17

all events leading to cGMP hydrolsis occurs in

membranes of disks

18

result of PDE activation

reduce cyto conc of cGMP, cGMP-gated channels close