For humans what is visible light spectrum?
390-700nm (peak of solar radiation spectrum)
What is the opsin gene family?
Gene family which receptors in animal eyes are based on, has 7 transmembrane helices
Why do photoreceptor cells have extensive membrane?
To accomodate as much rhodpsin as possible (the opsin in rods conserved from jellyfish to humans)
What type of photoreceptors are vertebrate rods and cones?
ciliary photoreceptors
What are the other type and where are they found?
microvillar photoreceptors, found in molluscs, stacks of microvilli form rhabdoms
Draw both
see internet – better than notes
Draw how retinaldehyde reacts to light
see notes
How does rhodopsin achieve amplification of the signal?
see diagram in notes
How does adaptation occur?
guanylate cyclase resynthesises cGMP
How does invertebrate phototransduction work?
activated rhodopsin acts through different Gprotein, Phospholipase c activated, cation channel opens(called TRP channel), depolarisation
What is exciting about opsin?
Can make opsins mechanically (requiring a retinal-based cofactor) which control an ion channel which can be opened or closed, controlled by photoabsorption, can be expressed in neurons where they control neural activity by shining a light on nerve cell –> optogenetics
in plants what is difference in light response?
No GCPRs instead direct electron transfer
