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Photoreceptors

QuestionAnswer
State the two components of rhodopsin. retinal and opsin
Describe the function of retinal? Light sensitive molecule in photoreceptor that absorbs photons.
State the name for the membrane proteins in photoreceptors. opsin
Describe the function of rod photoreceptors. Absorb light at low light intensities.
Describe the function of cone photoreceptors. Detects colours/wavelengths of light
Which type of photoreceptor has rhodopsin. Only rods
State the 4 different types of opsin? red, blue, green and UV (birds)
Explain how rods are well adapted to their function. Very high degree of amplification of a single photon.
Explain how cones are well adapted to their function. They have more than one type of opsin
Name the type of opsin found only in birds. UV
Describe what happens when a photon hits the retina. The photon is absorbed by rhodopsin changing its conformation to photoexcited rhodopsin.
Which molecule is a G protein: transducin or PDE. transducin
Which molecule is an enzyme: PDE or cGMP. PDE
State whether transducin or PDE activates the other molecule. transducin activates PDE
Describe what happens next after photoexcited rhodopsin is produced. Photoexcited rhodopsin activates 100’s of G protein molecules called transducin.
Describe what happens after 100's of transducin are activated Transducin activates 100’s of the enzyme PDE.
Describe what happens after 100's of PDE are activated. PDE hydrolyses 1000’s of molecules of cyclic GMP
Describe what happens after 1000's of cGMP are hydrolysed The hydrolysed cGMP comes off the ion channel which closes the channel.
Describe the two amplification steps in the rod pathway. 1 photoexcited rhodopsin activates 100's transducin AND 100's PDE hydrolyse 1000's cGMP
Created by: brightminds
 

 



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