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Phototransduction: Retina and Photoreceptor Rhodopsin Excitation - Recovery/adaptation

Phototransduction involves the following key steps: 1) Rhodopsin in photoreceptor cells is activated by light, initiating a signaling cascade. 2) This leads to activation of cyclic nucleotide-gated (CNG) channels in the photoreceptor cell membrane via a G protein and cyclic GMP. 3) The opening of CNG channels allows ions like sodium and calcium to flow into the cell, generating an electrical response and initiating neural signaling to the brain.

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Mega Hayyu Isfiati
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47 views5 pages

Phototransduction: Retina and Photoreceptor Rhodopsin Excitation - Recovery/adaptation

Phototransduction involves the following key steps: 1) Rhodopsin in photoreceptor cells is activated by light, initiating a signaling cascade. 2) This leads to activation of cyclic nucleotide-gated (CNG) channels in the photoreceptor cell membrane via a G protein and cyclic GMP. 3) The opening of CNG channels allows ions like sodium and calcium to flow into the cell, generating an electrical response and initiating neural signaling to the brain.

Uploaded by

Mega Hayyu Isfiati
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PPT, PDF, TXT or read online on Scribd
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Phototransduction

•Retina and photoreceptor

•Rhodopsin

•Excitation - recovery/adaptation

•Cyclic nucleotide gated channels

Eric Niederhoffer
SIU-SOM
Retina and Photoreceptor

http://www.fz-juelich.de/inb/inb-1/Photoreception/ http://www.mardre.com/homepage/mic/tem/samples/bio/ros/rosdiag.html
Rhodopsin
O
11 bathorhodopsin
H
12
lumirhodopsin

Rhodopsin* metarhodopsin I

h Metarhodopsin II (t1/2 ~ 60 s)
11
Opsin + trans-retinal
12

retinol RPE
O H

Rhodopsin cis-retinal
Excitation - Recovery/Adaptation
hv
GTP GMP
GDP
Ta I
Tbg Ta GTP CaM
Ta I CNGC
Rh GDP GTP
PDE PDE cGMP Na+
c-tR cGMP Ca2+

Rh RPE65 Excitation
tR cR
tR Recovery/Adaptation K+
RK
Rh Ca2+ Na+
Rc GC
tR
Low cGMP
[Ca2+] Arr
Low cGMP
[Ca2+] cGMP
GCAP-1
GTP
Review Questions

 Which ions and ion channels are used


for phototransduction?
 Which signal transduction pathway is
used for phototransduction (enzymes,
second messenger, receptor)?
 How does phototransduction compare
with gustation and olfaction?

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