There are two types of photoreceptors:

Rods 

Cones

TLS Online TPP Program

#Id: 9652

#Unit 4. Cell Communication and Cell Signaling

TLS Online TPP Program

#Id: 9653

#Unit 4. Cell Communication and Cell Signaling

Activated dimeric MAP kinase induces transcription of the c-fos gene by directly activating TCF, and indirectly activating SRF.

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Feedback regulation by MAP Kinase

activated MAP kinase phosphorylates the HER1 on a threonine residue near the juxtamembrane domain. 

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Feedback regulation by MAP Kinase

Phosphorylation of threonine residue in HER1 decreases the ability of the receptor kinase to become fully active.

TLS Online TPP Program

#Id: 9656

#Unit 4. Cell Communication and Cell Signaling

Feedback regulation by MAP Kinase

Active MAP kinase phosphorylates Raf on multiple sites, reducing its association with Ras.

TLS Online TPP Program

#Id: 9657

#Unit 4. Cell Communication and Cell Signaling

Negative feedback regulation by MAP Kinase

activated MAP kinase triggers an increase in the expression of dual-specificity phosphatases (DUSPs), particularly DUSP6.